feat: WorkOrderPhoto izolacija, upload modal i SN stupac u tablici putnih naloga

- Dodan WorkOrderPhoto model (FK na WorkOrder, odvojen od VehicleServicePhoto)
- Migracija 0022_workorderphoto
- WorkOrderViewSet.images action refaktoriran: GET/POST koristi WorkOrderPhoto
- WorkOrderPhotoSerializer dodan u serializers.py
- WorkOrderPhotoInline dodan u admin.py
- Novi WorkOrderPhotoUpload.jsx modal s podrskom za onBack prop i z-[60]
- WorkOrderDetailModal: gumb Dodaj fotografije u editMode, photoUploadOpen state,
  ispravljen onSuccess callback (map na URL stringove), reset pri zatvaranju
- FleetDashboardShell: stupac SN u tablici putnih naloga (craneInfo.crane_serial_number)
- fleetDashboardStore: uklonjen dupli toast iz uploadWorkOrderPhoto
- Dodan test test_work_order_images_endpoint.py

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

frontend/src/stores/fleetDashboardStore.js

@@ -607,6 +607,17 @@ export async function uploadServicePhoto(serviceRecordId, imageFile, description
     return response;
 }
 
+export async function uploadWorkOrderPhoto(workOrderId, imageFile, description = '', signal = null) {
+    const formData = new FormData();
+    formData.append('image', imageFile);
+    if (description.trim()) {
+        formData.append('description', description.trim());
+    }
+    const options = signal ? { signal } : {};
+    const response = await api.post(`fleet/work-orders/${encodeURIComponent(workOrderId)}/images/`, formData, options);
+    return response;
+}
+
 export async function uploadServiceAttachment(serviceRecordId, file, description = '', signal = null) {
     const formData = new FormData();
     formData.append('service_record', serviceRecordId);