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/PackingTemplateManager.tsx

@@ -159,7 +159,7 @@ export default function PackingTemplateManager() {
         </div>
         <button onClick={() => setShowCreate(true)}
           className="flex items-center gap-1.5 px-3 py-1.5 text-sm bg-slate-900 text-white rounded-lg hover:bg-slate-700 transition-colors">
-          <Plus className="w-4 h-4" /> {t('admin.packingTemplates.create')}
+          <Plus className="w-4 h-4" /> <span className="hidden sm:inline">{t('admin.packingTemplates.create')}</span>
         </button>
       </div>