feat: enhance date handling and indexing logic across connectors

- Added normalization for "undefined" strings to None in date parameters to prevent parsing errors.
- Improved date range validation to ensure start_date is strictly before end_date, adjusting end_date if necessary.
- Updated Google Calendar and Composio connector indexing logic to handle duplicate content more effectively, logging warnings for skipped events.
- Enhanced error handling during final commits to manage integrity errors gracefully.
- Refactored date handling in various connector indexers for consistency and reliability.

surfsense_backend/app/tasks/connector_indexers/base.py

@@ -112,6 +112,13 @@ def calculate_date_range(
     Returns:
         Tuple of (start_date_str, end_date_str)
     """
+    # Normalize "undefined" strings to None (from frontend)
+    # This prevents parsing errors and ensures consistent behavior across all indexers
+    if start_date == "undefined" or start_date == "":
+        start_date = None
+    if end_date == "undefined" or end_date == "":
+        end_date = None
+
     if start_date is not None and end_date is not None:
         return start_date, end_date