feat: per-task work hours table, notes, and read-only work order data in PDF page

Backend:
- Added service_report_note TextField to Task model (migration 0012)
- Exposed service_report_note in TaskSerializer
- task_service_context: fixed service record filter from
  work_order.vehicle_id -> task.vehicle_id (bug: cross-crane work orders
  returned wrong records for non-primary crane)
- task_service_context: include service_report_note in each task payload
- _build_work_order_service_records_docx_bytes: use per-task
  service_report_note (fallback: work_order.notes); fix service records
  query to use task vehicle ids for cross-crane support
- PDF generator: same per-task notes and cross-crane vehicle fix

Frontend:
- WorkOrderInvoicesPdfPage: removed global 'Uredi tablicu radnih sati' /
  'Uredi tekst napomene' buttons that always opened tasks[0]; replaced
  with per-task buttons inside each task article
- WorkOrderInvoicesPdfPage: separate editingTaskNote state / handler
  that calls updateTaskServiceReportNote (PATCH task.service_report_note)
- WorkOrderServiceNotesModal: now receives task prop instead of workOrder;
  reads/writes task.service_report_note; shows task title in header
- TaskWorkHoursTableModal: added workOrder prop; renders read-only amber
  info block with travel dates, mileage, and servicer vehicle data
- fleetDashboardStore: added updateTaskServiceReportNote() function
- WorkOrderInvoicesPdfPage: show saved service_report_note inline on
  each task card for quick reference

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

backend/modules/task_management/models.py

@@ -54,6 +54,12 @@ class Task(BaseModel):
         verbose_name=_("Planirani datum izvršenja"),
         help_text=_("Datum kada je planirano izvršenje radnog zadatka."),
     )
+    service_report_note = models.TextField(
+        blank=True,
+        default='',
+        verbose_name=_("Napomena izvještaja servisera"),
+        help_text=_("Tekst napomene za PDF izvještaj servisera za ovaj zadatak."),
+    )
 
     class Meta:
         ordering = ['-created_at']