fix: include user-owned work orders in monthly archive

Ensure monthly ZIP generation includes work orders owned by the user even when the task is assigned to someone else, and add a regression spec covering the user-owned work-order case.

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

backend/modules/fleet/tests/test_work_order_images_endpoint.py

@@ -639,6 +639,40 @@ class WorkOrderImagesEndpointTests(TestCase):
         self.assertNotIn('Liebherr LTM 1090', second_header)
         self.assertNotIn('MT150726', second_header)
 
+    def test_monthly_work_orders_archive_includes_work_orders_for_user_even_without_assigned_task(self):
+        other_user = get_user_model().objects.create_user(
+            username=f'wo-other-{uuid.uuid4().hex[:8]}',
+            email=f'wo-other-{uuid.uuid4().hex[:8]}@example.test',
+            password='test1234',
+        )
+        linked_work_order = WorkOrder.objects.create(
+            vehicle=self.vehicle,
+            creator=self.user,
+            display_code='MT170726',
+            purpose='kontrola',
+        )
+        Task.objects.create(
+            title='Zadatak drugog servisera',
+            assigned_to=other_user,
+            vehicle=self.vehicle,
+            work_order=linked_work_order,
+            scheduled_date=date(2033, 12, 20),
+        )
+        WorkOrderInvoice.objects.create(
+            work_order=linked_work_order,
+            naziv_racuna='Prosinac račun osoba',
+            datum='2033-12-12',
+            image=create_test_pdf('racun-prosinac-osoba.pdf'),
+            created_by=self.user,
+        )
+
+        response = self.client.get('/api/fleet/reports/monthly-work-orders-archive/?year=2033&month=12')
+        self.assertEqual(response.status_code, 200, response.content)
+
+        archive = zipfile.ZipFile(BytesIO(response.content))
+        self.assertIn('MT150726.work-order.pdf', archive.namelist())
+        self.assertIn('MT170726.work-order.pdf', archive.namelist())
+
     def test_monthly_work_orders_archive_contains_work_orders_and_invoices_folder(self):
         WorkOrderInvoice.objects.create(
             work_order=self.work_order,