fix: dohvat mjesecnih racuna za troskove

Uklanja ovisnost o workOrders.invoices i dohvaća račune direktno kroz API filtriran po mjesecu. Dodaje i display code putnog naloga u serializer kako bi prikaz u izvještaju ostao potpun.

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

backend/modules/fleet/views.py

@@ -3126,16 +3126,30 @@ class WorkOrderInvoiceViewSet(viewsets.ModelViewSet):
     def get_queryset(self):
         user = self.request.user
         work_order_id = self.request.query_params.get('work_order_id')
+        year = self.request.query_params.get('year')
+        month = self.request.query_params.get('month')
         qs = WorkOrderInvoice.objects.select_related('work_order', 'work_order__vehicle', 'created_by').filter(is_active=True)
+        if year and month:
+            try:
+                year_value = int(year)
+                month_value = int(month)
+            except (TypeError, ValueError):
+                year_value = None
+                month_value = None
+            if year_value and month_value and 1 <= month_value <= 12:
+                qs = qs.filter(
+                    work_order__work_order_tasks__scheduled_date__year=year_value,
+                    work_order__work_order_tasks__scheduled_date__month=month_value,
+                )
         if user.is_staff:
             if work_order_id:
                 qs = qs.filter(work_order_id=work_order_id)
-            return qs
+            return qs.distinct()
         allowed_orders = _work_orders_queryset_for_user(user).values('id')
         qs = qs.filter(work_order_id__in=allowed_orders)
         if work_order_id:
             qs = qs.filter(work_order_id=work_order_id)
-        return qs
+        return qs.distinct()
 
     def get_serializer_context(self):
         context = super().get_serializer_context()