fix(loyalty): terminal icons, server-side i18n, category in transactions

- Fix icons: plus-circle → plus, backspace → arrow-left
- Convert terminal $t() calls to server-side _() for card_label,
  stamps_until_reward, reward_label, not_enough_stamps
- Inject transaction type labels as server-rendered window._txLabels
  object (eliminates all async i18n warnings on terminal page)
- Resolve category_names in store transactions list endpoint

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

app/modules/loyalty/static/store/js/loyalty-terminal.js

@@ -369,9 +369,11 @@ function storeLoyaltyTerminal() {
         getTransactionLabel(tx) {
             const type = tx.transaction_type;
             if (type) {
-                return I18n.t('loyalty.transactions.' + type, {defaultValue: type.replace(/_/g, ' ')});
+                // Use server-rendered labels (no async flicker)
+                if (window._txLabels && window._txLabels[type]) return window._txLabels[type];
+                return type.replace(/_/g, ' ');
             }
-            return I18n.t('loyalty.common.unknown');
+            return 'Unknown';
         },
 
         getTransactionColor(tx) {