feat: Add Piper voice download helpers and guides

- Created download_piper_voices.py for automated download attempts
- Created download_piper_voices.sh as alternative bash script
- Created EASY_PIPER_SETUP.md with simple 3-step instructions
- Created PIPER_DOWNLOAD_GUIDE.md with visual step-by-step guide
- Includes troubleshooting, checklists, and pro tips

Makes Piper setup much easier for users with multiple guide options.

backend/EASY_PIPER_SETUP.md

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+# Easy Piper TTS Setup (5 Minutes)
+
+## The Problem
+
+Piper voice models can't be auto-downloaded due to HuggingFace's complex repository structure. But don't worry - manual download is quick and easy!
+
+## Quick Setup (3 Steps)
+
+### Step 1: Download Voice Files
+
+Visit this page: **https://github.com/rhasspy/piper/releases/tag/v1.2.0**
+
+Scroll down to "Assets" section and download these files:
+
+**Recommended Starter Pack (3 voices):**
+
+1. **en_US-lessac-medium** (Male, American)
+   - Download: `en_US-lessac-medium.onnx` (63 MB)
+   - Download: `en_US-lessac-medium.onnx.json` (8 KB)
+
+2. **en_US-amy-medium** (Female, American)
+   - Download: `en_US-amy-medium.onnx` (63 MB)
+   - Download: `en_US-amy-medium.onnx.json` (8 KB)
+
+3. **en_GB-alan-medium** (Male, British)
+   - Download: `en_GB-alan-medium.onnx` (63 MB)
+   - Download: `en_GB-alan-medium.onnx.json` (8 KB)
+
+**Total download:** ~190 MB for 3 voices
+
+### Step 2: Place Files
+
+Move all downloaded files to:
+```
+backend/piper_models/
+```
+
+Your directory should look like:
+```
+backend/piper_models/
+├── en_US-lessac-medium.onnx
+├── en_US-lessac-medium.onnx.json
+├── en_US-amy-medium.onnx
+├── en_US-amy-medium.onnx.json
+├── en_GB-alan-medium.onnx
+└── en_GB-alan-medium.onnx.json
+```
+
+### Step 3: Test
+
+```bash
+cd backend
+python test_piper_direct.py
+```
+
+You should see: "✓ Synthesis successful"
+
+## Done! 🎉
+
+Now you can:
+1. Start the backend: `uvicorn main:app --reload`
+2. Open the UI
+3. Click "Piper TTS" button
+4. Select Piper voices
+5. Generate audiobooks with pitch control!
+
+## More Voices (Optional)
+
+Want more variety? Download additional voices from the same page:
+
+**More American English:**
+- `en_US-libritts-high` (High quality, neutral)
+- `en_US-ryan-high` (Male, high quality)
+
+**More British English:**
+- `en_GB-alba-medium` (Female)
+- `en_GB-jenny_dioco-medium` (Female)
+
+**Other Languages:**
+- Browse the releases page for Spanish, French, German, etc.
+
+## Troubleshooting
+
+### "Model not found" error
+- Make sure you downloaded BOTH `.onnx` and `.onnx.json` files
+- Check files are in `backend/piper_models/` directory
+- Verify filenames match exactly (case-sensitive)
+
+### Files won't download
+- Try a different browser
+- Check your internet connection
+- Download one at a time if needed
+
+### Still having issues?
+- Fall back to Kokoro TTS (works out of the box)
+- Check `backend/PIPER_SETUP.md` for detailed troubleshooting
+
+## Why Manual Download?
+
+We tried automatic download but encountered:
+- ❌ Complex HuggingFace URL structure
+- ❌ SSL certificate issues
+- ❌ Unreliable across different systems
+
+Manual download is:
+- ✅ Fast (5 minutes)
+- ✅ Reliable (always works)
+- ✅ One-time setup
+- ✅ You control what you download
+
+## Alternative: Use Kokoro TTS
+
+If this seems like too much work, **Kokoro TTS works perfectly with zero setup**:
+- ✅ No downloads needed
+- ✅ 54 voices, 9 languages
+- ✅ High quality
+- ❌ No pitch control
+
+Just keep "Kokoro TTS" selected in the UI!
+
+## Need Help?
+
+1. Check the files are in the right place
+2. Run `python test_piper_direct.py` to diagnose
+3. Check backend logs for errors
+4. See `PIPER_STATUS.md` for more troubleshooting
+
+---
+
+**Remember:** This is a one-time setup. Once downloaded, Piper voices work forever! 🚀

backend/PIPER_DOWNLOAD_GUIDE.md

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+# Piper Voice Download - Visual Guide
+
+## 📥 Step-by-Step Instructions
+
+### Step 1: Go to Piper Releases Page
+
+Open this link in your browser:
+```
+https://github.com/rhasspy/piper/releases/tag/v1.2.0
+```
+
+### Step 2: Scroll to "Assets" Section
+
+Scroll down the page until you see a section called "Assets" with a list of files.
+
+### Step 3: Download Voice Files
+
+Click on each file to download (you need BOTH files for each voice):
+
+#### Voice 1: Male American (Lessac)
+- ✅ Click: `en_US-lessac-medium.onnx` (63 MB)
+- ✅ Click: `en_US-lessac-medium.onnx.json` (8 KB)
+
+#### Voice 2: Female American (Amy)
+- ✅ Click: `en_US-amy-medium.onnx` (63 MB)
+- ✅ Click: `en_US-amy-medium.onnx.json` (8 KB)
+
+#### Voice 3: Male British (Alan)
+- ✅ Click: `en_GB-alan-medium.onnx` (63 MB)
+- ✅ Click: `en_GB-alan-medium.onnx.json` (8 KB)
+
+**Total:** 6 files, ~190 MB
+
+### Step 4: Move Files to Models Directory
+
+1. Open your terminal
+2. Navigate to your project:
+   ```bash
+   cd /path/to/audiobook/backend
+   ```
+
+3. Create models directory if it doesn't exist:
+   ```bash
+   mkdir -p piper_models
+   ```
+
+4. Move downloaded files:
+   ```bash
+   # From your Downloads folder
+   mv ~/Downloads/en_US-*.onnx* piper_models/
+   mv ~/Downloads/en_GB-*.onnx* piper_models/
+   ```
+
+### Step 5: Verify Files
+
+Check that files are in place:
+```bash
+ls -lh piper_models/
+```
+
+You should see:
+```
+en_US-lessac-medium.onnx       (63 MB)
+en_US-lessac-medium.onnx.json  (8 KB)
+en_US-amy-medium.onnx          (63 MB)
+en_US-amy-medium.onnx.json     (8 KB)
+en_GB-alan-medium.onnx         (63 MB)
+en_GB-alan-medium.onnx.json    (8 KB)
+```
+
+### Step 6: Test Installation
+
+```bash
+python test_piper_direct.py
+```
+
+Expected output:
+```
+✓ Piper found
+✓ Model found: /path/to/piper_models/en_US-lessac-medium.onnx
+✓ Synthesis successful: XXXXX bytes of audio
+```
+
+## ✅ You're Done!
+
+Now you can use Piper TTS:
+
+1. **Start backend:**
+   ```bash
+   uvicorn main:app --reload
+   ```
+
+2. **Open frontend** in browser
+
+3. **Select "Piper TTS"** in Voice Assignment screen
+
+4. **Choose Piper voices** from dropdown
+
+5. **Generate audiobook** with pitch control!
+
+## 🎯 Quick Checklist
+
+- [ ] Downloaded 6 files (3 voices × 2 files each)
+- [ ] Moved files to `backend/piper_models/`
+- [ ] Verified files with `ls -lh piper_models/`
+- [ ] Tested with `python test_piper_direct.py`
+- [ ] Started backend server
+- [ ] Selected "Piper TTS" in UI
+
+## 🆘 Troubleshooting
+
+### Can't find files on GitHub?
+- Make sure you're on the v1.2.0 release page
+- Scroll down to "Assets" section
+- Files are listed alphabetically
+
+### Download fails?
+- Try a different browser
+- Check internet connection
+- Download one file at a time
+
+### Files in wrong place?
+```bash
+# Check current location
+pwd
+
+# Should show: /path/to/audiobook/backend
+
+# List models directory
+ls piper_models/
+```
+
+### Test fails?
+- Make sure BOTH .onnx and .onnx.json files are present
+- Check filenames match exactly (case-sensitive)
+- Verify Piper is installed: `piper --version`
+
+## 💡 Pro Tips
+
+1. **Download all at once:** Select all 6 files and download together
+2. **Use command line:** Faster to move files with `mv` command
+3. **Bookmark the page:** Easy to download more voices later
+4. **Try different voices:** Each has unique characteristics
+
+## 🔗 Useful Links
+
+- **Download Page:** https://github.com/rhasspy/piper/releases/tag/v1.2.0
+- **Voice Samples:** https://rhasspy.github.io/piper-samples/
+- **Full Setup Guide:** `PIPER_SETUP.md`
+- **Troubleshooting:** `PIPER_STATUS.md`
+
+---
+
+**Need more help?** Check `EASY_PIPER_SETUP.md` or ask for assistance!

backend/download_piper_voices.py

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+#!/usr/bin/env python3
+"""
+Simple script to download Piper TTS voice models.
+"""
+import os
+import sys
+import urllib.request
+import ssl
+
+# Create SSL context that doesn't verify (for development)
+ssl_context = ssl.create_default_context()
+ssl_context.check_hostname = False
+ssl_context.verify_mode = ssl.CERT_NONE
+
+# Models directory
+SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
+MODELS_DIR = os.path.join(SCRIPT_DIR, "piper_models")
+os.makedirs(MODELS_DIR, exist_ok=True)
+
+# Available voices with direct download links
+VOICES = {
+    "1": {
+        "name": "en_US-lessac-medium",
+        "description": "Male, American, Medium Quality",
+        "model_url": "https://huggingface.co/rhasspy/piper-voices/resolve/v1.0.0/en/en_US/en_US-lessac-medium.onnx",
+        "config_url": "https://huggingface.co/rhasspy/piper-voices/resolve/v1.0.0/en/en_US/en_US-lessac-medium.onnx.json",
+    },
+    "2": {
+        "name": "en_US-amy-medium",
+        "description": "Female, American, Medium Quality",
+        "model_url": "https://huggingface.co/rhasspy/piper-voices/resolve/v1.0.0/en/en_US/en_US-amy-medium.onnx",
+        "config_url": "https://huggingface.co/rhasspy/piper-voices/resolve/v1.0.0/en/en_US/en_US-amy-medium.onnx.json",
+    },
+    "3": {
+        "name": "en_US-libritts-high",
+        "description": "Neutral, American, High Quality",
+        "model_url": "https://huggingface.co/rhasspy/piper-voices/resolve/v1.0.0/en/en_US/en_US-libritts-high.onnx",
+        "config_url": "https://huggingface.co/rhasspy/piper-voices/resolve/v1.0.0/en/en_US/en_US-libritts-high.onnx.json",
+    },
+    "4": {
+        "name": "en_GB-alan-medium",
+        "description": "Male, British, Medium Quality",
+        "model_url": "https://huggingface.co/rhasspy/piper-voices/resolve/v1.0.0/en/en_GB/en_GB-alan-medium.onnx",
+        "config_url": "https://huggingface.co/rhasspy/piper-voices/resolve/v1.0.0/en/en_GB/en_GB-alan-medium.onnx.json",
+    },
+    "5": {
+        "name": "en_GB-alba-medium",
+        "description": "Female, British, Medium Quality",
+        "model_url": "https://huggingface.co/rhasspy/piper-voices/resolve/v1.0.0/en/en_GB/en_GB-alba-medium.onnx",
+        "config_url": "https://huggingface.co/rhasspy/piper-voices/resolve/v1.0.0/en/en_GB/en_GB-alba-medium.onnx.json",
+    },
+}
+
+
+def download_file(url, dest_path):
+    """Download a file with progress indication."""
+    try:
+        print(f"    Downloading from: {url}")
+        
+        # Use urllib with SSL context
+        with urllib.request.urlopen(url, context=ssl_context, timeout=120) as response:
+            total_size = int(response.headers.get('content-length', 0))
+            
+            with open(dest_path, 'wb') as f:
+                downloaded = 0
+                chunk_size = 8192
+                
+                while True:
+                    chunk = response.read(chunk_size)
+                    if not chunk:
+                        break
+                    
+                    f.write(chunk)
+                    downloaded += len(chunk)
+                    
+                    if total_size > 0:
+                        percent = (downloaded / total_size) * 100
+                        print(f"\r    Progress: {percent:.1f}% ({downloaded}/{total_size} bytes)", end='')
+        
+        print()  # New line after progress
+        
+        # Verify file size
+        file_size = os.path.getsize(dest_path)
+        if file_size < 1000:
+            print(f"    ✗ Download failed (file too small: {file_size} bytes)")
+            os.remove(dest_path)
+            return False
+        
+        print(f"    ✓ Downloaded: {file_size:,} bytes")
+        return True
+        
+    except Exception as e:
+        print(f"    ✗ Error: {e}")
+        if os.path.exists(dest_path):
+            os.remove(dest_path)
+        return False
+
+
+def download_voice(voice_key):
+    """Download a voice model and config."""
+    voice = VOICES[voice_key]
+    name = voice["name"]
+    
+    model_path = os.path.join(MODELS_DIR, f"{name}.onnx")
+    config_path = os.path.join(MODELS_DIR, f"{name}.onnx.json")
+    
+    # Check if already exists
+    if os.path.exists(model_path) and os.path.exists(config_path):
+        print(f"  ✓ {name} - Already downloaded")
+        return True
+    
+    print(f"\n  Downloading: {name}")
+    print(f"  Description: {voice['description']}")
+    
+    # Download model
+    print("  [1/2] Model file (.onnx)...")
+    if not download_file(voice["model_url"], model_path):
+        return False
+    
+    # Download config
+    print("  [2/2] Config file (.onnx.json)...")
+    if not download_file(voice["config_url"], config_path):
+        return False
+    
+    print(f"  ✓ {name} - Complete!")
+    return True
+
+
+def main():
+    print("=" * 60)
+    print("Piper TTS Voice Model Downloader")
+    print("=" * 60)
+    print(f"\nModels directory: {MODELS_DIR}\n")
+    
+    print("Available voices:\n")
+    for key, voice in VOICES.items():
+        print(f"  {key}) {voice['name']}")
+        print(f"     {voice['description']}")
+        print()
+    
+    print("Quick options:")
+    print("  a) Download all voices (recommended)")
+    print("  s) Download starter pack (1, 2, 4)")
+    print("  q) Quit")
+    print()
+    
+    choice = input("Enter your choice (1-5, a, s, or q): ").strip().lower()
+    
+    if choice == 'q':
+        print("Exiting...")
+        return
+    
+    print("\n" + "=" * 60)
+    print("Downloading...")
+    print("=" * 60)
+    
+    success_count = 0
+    total_count = 0
+    
+    if choice == 'a':
+        # Download all
+        for key in VOICES.keys():
+            total_count += 1
+            if download_voice(key):
+                success_count += 1
+    elif choice == 's':
+        # Starter pack
+        for key in ['1', '2', '4']:
+            total_count += 1
+            if download_voice(key):
+                success_count += 1
+    elif choice in VOICES:
+        # Single voice
+        total_count += 1
+        if download_voice(choice):
+            success_count += 1
+    else:
+        print(f"Invalid choice: {choice}")
+        return
+    
+    print("\n" + "=" * 60)
+    print("Download Summary")
+    print("=" * 60)
+    print(f"\nSuccessfully downloaded: {success_count}/{total_count} voices")
+    
+    # List downloaded files
+    print(f"\nFiles in {MODELS_DIR}:")
+    try:
+        files = sorted(os.listdir(MODELS_DIR))
+        if files:
+            for f in files:
+                size = os.path.getsize(os.path.join(MODELS_DIR, f))
+                print(f"  {f} ({size:,} bytes)")
+        else:
+            print("  (empty)")
+    except Exception as e:
+        print(f"  Error listing files: {e}")
+    
+    print("\n" + "=" * 60)
+    print("Next Steps")
+    print("=" * 60)
+    print("\n1. Test Piper installation:")
+    print("   python test_piper_direct.py")
+    print("\n2. Start the backend:")
+    print("   uvicorn main:app --reload")
+    print("\n3. In the UI, click 'Piper TTS' button")
+    print("\n4. Select a Piper voice and generate!")
+    print()
+
+
+if __name__ == "__main__":
+    try:
+        main()
+    except KeyboardInterrupt:
+        print("\n\nDownload cancelled by user.")
+        sys.exit(1)
+    except Exception as e:
+        print(f"\n\nError: {e}")
+        sys.exit(1)

backend/download_piper_voices.sh

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+#!/bin/bash
+# Helper script to download Piper TTS voice models
+
+set -e
+
+echo "=================================================="
+echo "Piper TTS Voice Model Downloader"
+echo "=================================================="
+echo ""
+
+# Create models directory
+MODELS_DIR="$(dirname "$0")/piper_models"
+mkdir -p "$MODELS_DIR"
+echo "✓ Models directory: $MODELS_DIR"
+echo ""
+
+# Base URL for Piper voices
+BASE_URL="https://huggingface.co/rhasspy/piper-voices/resolve/main"
+
+# Function to download a voice
+download_voice() {
+    local voice_id=$1
+    local lang_code=$2
+    
+    echo "Downloading $voice_id..."
+    
+    # Construct URLs
+    local model_url="${BASE_URL}/${lang_code}/${lang_code}_${voice_id}.onnx"
+    local config_url="${BASE_URL}/${lang_code}/${lang_code}_${voice_id}.onnx.json"
+    
+    local model_file="${MODELS_DIR}/${lang_code}-${voice_id}.onnx"
+    local config_file="${MODELS_DIR}/${lang_code}-${voice_id}.onnx.json"
+    
+    # Check if already exists
+    if [ -f "$model_file" ] && [ -f "$config_file" ]; then
+        echo "  ✓ Already downloaded"
+        return 0
+    fi
+    
+    # Download with curl
+    if command -v curl &> /dev/null; then
+        echo "  Downloading model file..."
+        curl -L -o "$model_file" "$model_url" 2>/dev/null || {
+            echo "  ✗ Failed to download model"
+            return 1
+        }
+        
+        echo "  Downloading config file..."
+        curl -L -o "$config_file" "$config_url" 2>/dev/null || {
+            echo "  ✗ Failed to download config"
+            return 1
+        }
+        
+        # Verify files are not error pages
+        if [ $(wc -c < "$model_file") -lt 1000 ]; then
+            echo "  ✗ Download failed (file too small)"
+            rm -f "$model_file" "$config_file"
+            return 1
+        fi
+        
+        echo "  ✓ Downloaded successfully"
+        return 0
+    else
+        echo "  ✗ curl not found"
+        return 1
+    fi
+}
+
+echo "Select voices to download:"
+echo ""
+echo "Recommended starter pack (3 voices):"
+echo "  1) en_US-lessac-medium (Male, American)"
+echo "  2) en_US-amy-medium (Female, American)"
+echo "  3) en_GB-alan-medium (Male, British)"
+echo ""
+echo "All English voices (5 voices):"
+echo "  4) All of the above + 2 more"
+echo ""
+echo "Manual selection:"
+echo "  5) Choose specific voices"
+echo ""
+echo "  0) Exit"
+echo ""
+read -p "Enter your choice (0-5): " choice
+
+case $choice in
+    1)
+        echo ""
+        echo "Downloading starter pack..."
+        echo ""
+        download_voice "lessac-medium" "en_US"
+        download_voice "amy-medium" "en_US"
+        download_voice "alan-medium" "en_GB"
+        ;;
+    2)
+        echo ""
+        echo "Downloading all English voices..."
+        echo ""
+        download_voice "lessac-medium" "en_US"
+        download_voice "amy-medium" "en_US"
+        download_voice "libritts-high" "en_US"
+        download_voice "alan-medium" "en_GB"
+        download_voice "alba-medium" "en_GB"
+        ;;
+    3)
+        echo ""
+        echo "Available voices:"
+        echo "  en_US-lessac-medium (Male, American)"
+        echo "  en_US-amy-medium (Female, American)"
+        echo "  en_US-libritts-high (Neutral, American, High Quality)"
+        echo "  en_GB-alan-medium (Male, British)"
+        echo "  en_GB-alba-medium (Female, British)"
+        echo ""
+        echo "Enter voice IDs separated by spaces (e.g., lessac-medium amy-medium):"
+        read -p "> " voices
+        
+        for voice in $voices; do
+            if [[ $voice == *"GB"* ]]; then
+                download_voice "$voice" "en_GB"
+            else
+                download_voice "$voice" "en_US"
+            fi
+        done
+        ;;
+    0)
+        echo "Exiting..."
+        exit 0
+        ;;
+    *)
+        echo "Invalid choice"
+        exit 1
+        ;;
+esac
+
+echo ""
+echo "=================================================="
+echo "Download Summary"
+echo "=================================================="
+echo ""
+echo "Downloaded files in: $MODELS_DIR"
+ls -lh "$MODELS_DIR" 2>/dev/null || echo "No files found"
+echo ""
+echo "✓ Setup complete!"
+echo ""
+echo "Next steps:"
+echo "  1. Test Piper: python test_piper_direct.py"
+echo "  2. Start backend: uvicorn main:app --reload"
+echo "  3. Select 'Piper TTS' in the UI"
+echo ""