fix(loyalty): resolve critical production readiness issues

- Add pessimistic locking (SELECT FOR UPDATE) on card write operations
  to prevent race conditions in stamp_service and points_service
- Replace 16 console.log/error/warn calls with LogConfig.createLogger()
  in 3 storefront JS files (dashboard, history, enroll)
- Delete all stale lu.json locale files across 8 modules (lb is the
  correct ISO 639-1 code for Luxembourgish)
- Update architecture rules and docs to reference lb.json not lu.json
- Add production-readiness.md report for loyalty module

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/modules/loyalty/services/card_service.py

@@ -52,6 +52,19 @@ class CardService:
             .first()
         )
 
+    def get_card_for_update(self, db: Session, card_id: int) -> LoyaltyCard | None:
+        """Get a loyalty card by ID with a row-level lock (SELECT ... FOR UPDATE).
+
+        Note: Does not use joinedload to avoid LEFT OUTER JOIN which is
+        incompatible with FOR UPDATE in PostgreSQL.
+        """
+        return (
+            db.query(LoyaltyCard)
+            .filter(LoyaltyCard.id == card_id)
+            .with_for_update()
+            .first()
+        )
+
     def get_card_by_qr_code(self, db: Session, qr_code: str) -> LoyaltyCard | None:
         """Get a loyalty card by QR code data."""
         return (