feat: enhance backend security and configuration

- Updated Dockerfile to improve security with a non-root user and added health checks.
- Modified docker-compose.yml to set containers as read-only, restrict ports to localhost, and implement health checks.
- Enhanced .env.example with additional environment variables for security and configuration.
- Improved FastAPI application with middleware for security headers, CORS, and body size limits.
- Refactored authentication flow in auth.py to include state validation and improved error handling.
- Added rate limiting to various endpoints to prevent abuse.
- Updated researcher and publication handling to ensure better validation and error management.

backend/.dockerignore

@@ -0,0 +1,20 @@
+.env
+.env.*
+!.env.example
+__pycache__/
+*.pyc
+*.pyo
+*.pyd
+*.log
+*.sqlite3
+*.db
+.pytest_cache/
+.mypy_cache/
+.ruff_cache/
+.venv/
+venv/
+.git/
+.gitignore
+README.md
+docs/
+tests/