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>

frontend/src/stores/fleetDashboardStore.js

@@ -771,6 +771,17 @@ export async function updateTaskWorkHoursTable(taskId, data) {
     return payload;
 }
 
+export async function updateTaskServiceReportNote(taskId, note) {
+    if (!taskId) {
+        throw new Error('Task ID je obavezan.');
+    }
+    const payload = await api.patch(`tasks/tasks/${encodeURIComponent(taskId)}/`, {
+        service_report_note: String(note ?? ''),
+    });
+    showToast('Napomena servisnog izvještaja je uspješno spremljena.', 'success');
+    return payload;
+}
+
 export async function createWorkOrderInvoice(workOrderId, data = {}, signal = null) {
     if (!workOrderId) {
         throw new Error('Work order ID je obavezan.');