Update main.py

main.py

@@ -98,7 +98,10 @@ LEAVE_TYPES = ["annual", "sick", "maternity", "paternity", "unpaid", "study", "c
 LEAVE_STATUSES = ["pending", "approved", "declined", "cancelled"]
 MEETING_STATUSES = ["scheduled", "in_progress", "completed", "cancelled"]
 EXPENSE_STATUSES = ["pending", "approved", "flagged", "rejected"]
-SUBMISSION_WEEK_FORMAT = "%Y-W%W"   # e.g. 2026-W20
+SUBMISSION_WEEK_FORMAT = "%G-W%V"   # ISO 8601 week: %G = ISO year, %V = ISO week number (Mon-based)
+                                    # Matches TypeScript's getISOWeek() output exactly e.g. "2026-W21"
+                                    # %W (old value) was Monday-based week-of-year per Python locale,
+                                    # which diverges from ISO by 1 on most dates — fixed here.
 
 
 # =============================================================================
@@ -131,7 +134,7 @@ try:
         raise ValueError("'Gemini' env var not set.")
     from google import genai
     gemini_client = genai.Client(api_key=_gemini_key)
-    MODEL_NAME = "gemini-2.5-flash"
+    MODEL_NAME = "gemini-3.1-flash-lite"
     logger.info(f"Gemini initialized ({MODEL_NAME}).")
 except Exception as e:
     logger.critical(f"FATAL Gemini init: {e}")