feat(loyalty): translatable categories + mandatory on earn points

- Add name_translations JSON column to StoreTransactionCategory
  (migration loyalty_008). Stores {"en": "Men", "fr": "Hommes", ...}.
  Model has get_translated_name(lang) helper.
- Admin CRUD form now has FR/DE/LB translation inputs alongside the
  default name.
- Points earn: category_id is now mandatory when the store has
  active categories configured. Returns CATEGORY_REQUIRED error.
- Stamps: category remains optional (quick tap workflow).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/modules/loyalty/services/points_service.py

@@ -23,6 +23,7 @@ from app.modules.loyalty.exceptions import (
     InsufficientPointsException,
     InvalidRewardException,
     LoyaltyCardInactiveException,
+    LoyaltyException,
     LoyaltyProgramInactiveException,
     OrderReferenceRequiredException,
     StaffPinRequiredException,
@@ -102,6 +103,19 @@ class PointsService:
         if settings and settings.require_order_reference and not order_reference:
             raise OrderReferenceRequiredException()
 
+        # Category is mandatory when the store has categories configured
+        if not category_id:
+            from app.modules.loyalty.services.category_service import category_service
+
+            store_categories = category_service.list_categories(
+                db, store_id, active_only=True
+            )
+            if store_categories:
+                raise LoyaltyException(
+                    message="Please select a product category",
+                    error_code="CATEGORY_REQUIRED",
+                )
+
         # Idempotency guard: if same order_reference already earned points on this card, return existing result
         if order_reference:
             existing_tx = (