Containerize backend with Docker Compose

Added Docker support for easy deployment:
- Dockerfile: Python 3.11 slim image with FastAPI app
- docker-compose.yml: Service definition with volume mounting for data persistence
- .dockerignore: Exclude unnecessary files from Docker build
- database.py: Updated to store SQLite DB in ./data directory for volume persistence
- .gitignore: Added entries for database files and data directory
- README.md: Comprehensive documentation with Docker and local setup instructions

The application can now be run with: docker compose up -d
Database persists in ./data directory mounted as a volume

Dockerfile

@@ -0,0 +1,19 @@
+FROM python:3.11-slim
+
+# Set working directory
+WORKDIR /app
+
+# Copy requirements first for better caching
+COPY requirements.txt .
+
+# Install dependencies
+RUN pip install --no-cache-dir -r requirements.txt
+
+# Copy application code
+COPY . .
+
+# Expose port
+EXPOSE 8000
+
+# Run the application
+CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]