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

@@ -0,0 +1,130 @@
+# 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! 🚀