feat: bag tracking with weight distribution, packing UX overhaul — closes #13

- Bag tracking: optional admin setting under Packing addon, weight per item,
  bag assignment with inline creation, iOS-style weight sidebar + mobile modal
- Admin: merged Categories + Packing Templates into "Configuration" tab
- Packing UI: category-first workflow, mobile-friendly action buttons,
  stable category ordering, responsive button labels

client/src/components/Admin/CategoryManager.tsx

@@ -198,7 +198,6 @@ export default function CategoryManager() {
           className="flex items-center gap-2 bg-slate-900 text-white px-3 sm:px-4 py-2 rounded-lg hover:bg-slate-700 text-sm font-medium">
           <Plus className="w-4 h-4" />
           <span className="hidden sm:inline">{t('categories.new')}</span>
-          <span className="sm:hidden">Add</span>
         </button>
       </div>