- Added a global exception handler to log unhandled exceptions and return a generic 500 JSON response without exposing details to the client.
- Updated the configuration to validate the `DATABASE_URL` format, ensuring it starts with `sqlite://` or `postgresql://`, and log warnings for invalid formats.
- Introduced safe parsing for numeric environment variables (`HTTP_PORT`, `INIT_DATA_MAX_AGE_SECONDS`) with defaults on invalid values, including logging warnings for out-of-range values.
- Enhanced the duty schedule parser to enforce limits on the number of schedule rows and the length of full names and duty strings, raising appropriate errors when exceeded.
- Updated internationalization messages to include generic error responses for import failures and parsing issues, improving user experience.
- Added unit tests to verify the new error handling and configuration validation behaviors.
- Added AGENTS.md for AI agent documentation and maintainers, outlining project structure and conventions.
- Updated CONTRIBUTING.md to specify that all project documentation must be in English, including README and docstrings.
- Enhanced README.md to reference documentation guidelines and the new AGENTS.md file.
- Cleaned up .gitignore by removing unnecessary entries for cursor-related files.
- Introduced new .cursor rules for backend, frontend, project architecture, and testing to standardize development practices.
