feat: port inventory (انبارداری) page from tauri to admin dashboard

Add a per-tenant (doctor/clinic) Inventory domain and admin page, ported
from clinic-pro-tauri /inventory (which was static/mock) into a real feature.

Backend (src/Inventory/):
- Entities InventoryItem, InventoryPackage, InventoryPackageItem, scoped via
  entity_type/entity_id like TenantTag. Item status is derived, package total
  and availability derived at read time.
- InventoryService (stats, package assembly, availability), thin
  InventoryController with CRUD for items and packages + categories endpoint.
- Migration + docs/api/inventory.md + functional tests (10 tests, 42 assertions).

Frontend (assets/admin/):
- InventoryPage with two tabs (کالاهای مصرفی / پکیج), stat cards, items table
  (desktop + mobile cards), packages accordion, add/edit item and package
  modals, search + category filter — pixel-matched to the tauri source.
- useInventory hook (TanStack Query), route + sidebar link for doctor/clinic.
- Vitest coverage (real data, empty state, modal, packages tab).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

assets/admin/App.tsx

@@ -58,6 +58,7 @@ import AccountSettingsPage from './pages/AccountSettingsPage';
 import TagsSettingsPage from './pages/TagsSettingsPage';
 import AppointmentSettingsPage from './pages/AppointmentSettingsPage';
 import PatientsListPage from './pages/PatientsListPage';
+import InventoryPage from './pages/InventoryPage';
 import PatientRecordFormPage from './pages/PatientRecordFormPage';
 import PatientDetailPage from './pages/PatientDetailPage';
 import PaymentSuccessPage from './pages/PaymentSuccessPage';
@@ -221,6 +222,7 @@ export default function App() {
         <Route path="subscription" element={<RoleRoute roles={['doctor', 'clinic']} blockClinicScope><SubscriptionPage /></RoleRoute>} />
         <Route path="subscription/success" element={<RoleRoute roles={['doctor', 'clinic']} blockClinicScope><PaymentSuccessPage /></RoleRoute>} />
         <Route path="clinic-services" element={<RoleRoute roles={['doctor', 'clinic']} blockClinicScope><ClinicServicesPage /></RoleRoute>} />
+        <Route path="inventory" element={<RoleRoute roles={['doctor', 'clinic']} blockClinicScope><InventoryPage /></RoleRoute>} />
         <Route path="sms-wallet" element={<RoleRoute roles={['doctor', 'clinic']} blockClinicScope><SmsWalletPage /></RoleRoute>} />
         <Route path="my-secretaries" element={<RoleRoute roles={['doctor', 'clinic']} blockClinicScope><MySecretariesPage /></RoleRoute>} />
         <Route path="admin-subscription" element={<RoleRoute roles={['admin']}><AdminSubscriptionPage /></RoleRoute>} />