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