feat: configure docker image deployment with Gitea Container Registry

- Replace local build with pre-built image from Gitea registry
- Add docker-compose.override.yml for local development with Dockerfile
- Add .dockerignore to exclude unnecessary files from build
- Update image reference to gitea.onecluster.org/oneteam/don_confiao_backend:latest

Refs #37

.dockerignore

@@ -0,0 +1,17 @@
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
+.Python
+*.db
+*.sqlite3
+.env
+.venv
+venv/
+ENV/
+.git/
+*.egg-info/
+dist/
+build/
+.coverage
+htmlcov/