feat(loyalty): category view mode + mandatory translations

- Add eye icon to expand read-only view of all translations
- View panel shows EN/FR/DE/LB values with "Edit" button to switch
  to edit mode
- All 4 language fields (EN/FR/DE/LB) now mandatory — Save button
  disabled until all are filled (both add and edit forms)

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

app/modules/loyalty/static/admin/js/loyalty-merchant-detail.js

@@ -39,6 +39,7 @@ function adminLoyaltyMerchantDetail() {
         showAddCategory: false,
         newCategoryName: '',
         newCategoryTranslations: { fr: '', de: '', lb: '' },
+        viewingCategoryId: null,
         editingCategoryId: null,
         editCategoryData: { name: '', translations: { fr: '', de: '', lb: '' } },