feat: Add Phase 5 store configuration UI

- Built StoreConfigView.vue for webstore setup
- Form fields: store name, description, currency (USD/EUR/GBP)
- PayPal credentials (client ID/secret) with encryption support
- Sandbox/production mode toggle with warning states
- Store enable/disable with validation
- Empty state for unconfigured stores
- TypeScript StoreConfig interface
- Route: /admin/webstore/config (auth required)
- API integration: GET/PUT /api/webstore/config
- Responsive Tailwind design

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

frontend/src/router/index.ts

@@ -159,6 +159,11 @@ const panelRoutes: RouteRecordRaw[] = [
         name: 'team',
         component: () => import('@/views/admin/TeamView.vue'),
       },
+      {
+        path: 'store/config',
+        name: 'store-config',
+        component: () => import('@/views/admin/StoreConfigView.vue'),
+      },
       {
         path: 'store/manage',
         name: 'store-manage',