feat: dozvoli dijeljenje putnog naloga izmedju razlicitih dizalica

Problem: serviser nije mogao odabrati putni nalog kreiran za drugu dizalicu
jer je frontend filtrirao naloge po aktivnom crane kontekstu, a backend
serializer je bacao ValidationError ako WO.vehicle != task.vehicle.

Promjene:
- TaskSerializer: uklonjena cross-crane validacija - WO moze pripadati
  drugoj dizalici od one na tasku (cross-crane sharing)
- FleetDashboardShell: serviceRecordWorkOrders i selectedTaskWorkOrders
  vise ne filtriraju po vehicle ID-u, prikazuju sve otvorene naloge
- TaskServiceRecordsModal: gumb i modal za izmjenu podataka dizalice
  (radni sati, kilometraza) premjesten iz WorkOrderDetailModal
- WorkOrderDetailModal: uklonjen gumb 'Izmijeni podatke dizalice'
- Dodana 3 nova backend testa za cross-crane WO dodjelu (15/15 prolaze)

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

backend/modules/task_management/serializers.py

@@ -146,13 +146,12 @@ class TaskSerializer(serializers.ModelSerializer):
                 'title': "Naslov zadatka je obavezan ako se task ne kreira iz templatea."
             })
 
+        # If task has no crane yet, auto-derive it from the work order's crane (backward compat).
+        # Cross-crane assignment is intentionally allowed: a servicer can share one work order
+        # across tasks for multiple cranes on the same day.
         if work_order and not vehicle:
             vehicle = work_order.vehicle
             attrs['vehicle'] = vehicle
-        if work_order and vehicle and work_order.vehicle_id != vehicle.id:
-            raise serializers.ValidationError({
-                'work_order': "Putni nalog mora pripadati istoj dizalici kao task."
-            })
 
         if status_value in {'neaktivan', 'zavrsen'} and not work_order:
             raise serializers.ValidationError({