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/utils/dates.py

@@ -24,10 +24,17 @@ def duty_to_iso(d: date, hour_utc: int, minute_utc: int) -> str:
 _ISO_DATE_RE = re.compile(r"^\d{4}-\d{2}-\d{2}$")
 
 
+# Maximum allowed date range in days (e.g. 731 = 2 years).
+MAX_DATE_RANGE_DAYS = 731
+
+
 class DateRangeValidationError(ValueError):
     """Raised when from_date/to_date validation fails. API uses kind for i18n key."""
 
-    def __init__(self, kind: Literal["bad_format", "from_after_to"]) -> None:
+    def __init__(
+        self,
+        kind: Literal["bad_format", "from_after_to", "range_too_large"],
+    ) -> None:
         self.kind = kind
         super().__init__(kind)
 
@@ -86,12 +93,20 @@ def parse_iso_date(s: str) -> date | None:
 
 
 def validate_date_range(from_date: str, to_date: str) -> None:
-    """Validate from_date and to_date are YYYY-MM-DD and from_date <= to_date.
+    """Validate from_date and to_date are YYYY-MM-DD, from_date <= to_date, and range <= MAX_DATE_RANGE_DAYS.
 
     Raises:
-        DateRangeValidationError: bad_format if format invalid, from_after_to if from > to.
+        DateRangeValidationError: bad_format if format invalid, from_after_to if from > to,
+            range_too_large if (to_date - from_date) > MAX_DATE_RANGE_DAYS.
     """
     if not _ISO_DATE_RE.match(from_date or "") or not _ISO_DATE_RE.match(to_date or ""):
         raise DateRangeValidationError("bad_format")
     if from_date > to_date:
         raise DateRangeValidationError("from_after_to")
+    try:
+        from_d = date.fromisoformat(from_date)
+        to_d = date.fromisoformat(to_date)
+    except ValueError:
+        raise DateRangeValidationError("bad_format") from None
+    if (to_d - from_d).days > MAX_DATE_RANGE_DAYS:
+        raise DateRangeValidationError("range_too_large")