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>

backend/modules/fleet/admin.py

@@ -5,6 +5,7 @@ from .models import (
     Crane,
     Vehicle,
     WorkOrder,
+    WorkOrderPhoto,
     WorkOrderInvoice,
     VehicleServiceRecord,
     VehicleServicePhoto,
@@ -60,6 +61,26 @@ class WorkOrderInvoiceInline(admin.TabularInline):
     readonly_fields = ('created_at',)
 
 
+class WorkOrderPhotoInline(admin.TabularInline):
+    model = WorkOrderPhoto
+    extra = 0
+    fields = ('thumbnail_preview', 'image', 'description', 'uploaded_by', 'created_at', 'is_active')
+    readonly_fields = ('thumbnail_preview', 'created_at')
+    show_change_link = True
+
+    @admin.display(description="Pregled")
+    def thumbnail_preview(self, obj):
+        if obj.image:
+            return format_html(
+                '<a href="{}" target="_blank">'
+                '<img src="{}" style="height:64px;width:auto;border-radius:4px;object-fit:cover;" />'
+                '</a>',
+                obj.image.url,
+                obj.image.url,
+            )
+        return "—"
+
+
 @admin.register(Vehicle)
 class VehicleAdmin(admin.ModelAdmin):
     list_display = (
@@ -159,7 +180,7 @@ class WorkOrderAdmin(admin.ModelAdmin):
     search_fields = ('vehicle__registration_number', 'creator__username', 'purpose')
     readonly_fields = ('date',)
     ordering = ('-date',)
-    inlines = (WorkOrderInvoiceInline,)
+    inlines = (WorkOrderInvoiceInline, WorkOrderPhotoInline)
 
     def distance_display(self, obj):
         return obj.distance