feat: enhance error handling and configuration validation

- 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.

duty_teller/api/dependencies.py

@@ -42,7 +42,12 @@ def _validate_duty_dates(from_date: str, to_date: str, lang: str) -> None:
     try:
         validate_date_range(from_date, to_date)
     except DateRangeValidationError as e:
-        key = "dates.bad_format" if e.kind == "bad_format" else "dates.from_after_to"
+        key_map = {
+            "bad_format": "dates.bad_format",
+            "from_after_to": "dates.from_after_to",
+            "range_too_large": "dates.range_too_large",
+        }
+        key = key_map.get(e.kind, "dates.bad_format")
         raise HTTPException(status_code=400, detail=t(lang, key)) from e
     except ValueError as e:
         # Backward compatibility if something else raises ValueError.