chore: update Docker configuration and improve health check functionality

- Added Docker health check endpoint to the FastAPI application, returning a 200 status when the app is running.
- Updated Dockerfile to include curl for health checks and modified entrypoint script to exit on errors.
- Enhanced .dockerignore and .gitignore files to exclude coverage and test artifacts.
- Updated docker-compose.prod.yml to specify version.
- Added pytest-cov as a development dependency to improve test coverage reporting.

entrypoint.sh

@@ -1,5 +1,5 @@
 #!/bin/sh
-set -e
+set -eu
 # Ensure data dir exists and is writable by botuser (volume may be root-owned)
 mkdir -p /app/data
 chown botuser:botuser /app/data