feat: Add Docker configuration for backend

- Create Dockerfile with Python 3.10 base image
- Install system dependencies (espeak-ng) for Kokoro TTS
- Install Python dependencies from requirements.txt
- Copy backend code and expose port 8000
- Configure Uvicorn server startup
- Add docker-compose.yml for easy orchestration
- Include health checks and environment variables
- Add .dockerignore to optimize build context

Implements task 6 - Requirements 11.1-11.6

backend/.dockerignore

@@ -0,0 +1,36 @@
+# Python
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
+.Python
+venv/
+env/
+ENV/
+.venv
+
+# Testing
+.pytest_cache/
+*.log
+test_*.py
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+
+# Environment
+.env
+.env.local
+
+# Git
+.git/
+.gitignore
+
+# Documentation
+README.md
+
+# Other
+*.md
+!requirements.txt

backend/Dockerfile

@@ -0,0 +1,35 @@
+# Use Python 3.10 as base image
+FROM python:3.10-slim
+
+# Set working directory
+WORKDIR /app
+
+# Install system dependencies
+# espeak-ng is required for Kokoro TTS (grapheme-to-phoneme conversion)
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends \
+    espeak-ng \
+    && rm -rf /var/lib/apt/lists/*
+
+# Copy requirements file
+COPY requirements.txt .
+
+# Install Python dependencies
+RUN pip install --no-cache-dir -r requirements.txt
+
+# Copy backend code
+COPY . .
+
+# Expose port 8000
+EXPOSE 8000
+
+# Set environment variables
+ENV PORT=8000
+ENV LOG_LEVEL=info
+
+# Health check
+HEALTHCHECK --interval=30s --timeout=10s --start-period=40s --retries=3 \
+    CMD python -c "import urllib.request; urllib.request.urlopen('http://localhost:8000/api/health')"
+
+# Start Uvicorn server
+CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]

backend/docker-compose.yml

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+version: '3.8'
+
+services:
+  backend:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    container_name: text-to-audiobook-backend
+    ports:
+      - "8000:8000"
+    environment:
+      - PORT=8000
+      - LOG_LEVEL=info
+    volumes:
+      # Mount code for development (optional - comment out for production)
+      - ./services:/app/services
+      - ./main.py:/app/main.py
+    restart: unless-stopped
+    healthcheck:
+      test: ["CMD", "python", "-c", "import urllib.request; urllib.request.urlopen('http://localhost:8000/api/health')"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+      start_period: 40s