feat: dodaj dodatne troškove s OCR sinkronizacijom

Dodana je tablica DODATNI TROŠKOVI za putni nalog (backend model + API +
frontend modal) s izračunom ukupnog iznosa za isplatu.

Upload računa sada odmah upisuje redak u dodatne troškove, a asinkroni OCR
(Celery) naknadno pokušava popuniti broj računa i iznos iz slike/PDF-a.

Uvedena je invalidacija PDF cache-a nakon promjena računa/dodatnih troškova
kako bi generirani PDF uvijek prikazivao najnovije podatke.

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

frontend/src/stores/fleetDashboardStore.js

@@ -712,10 +712,32 @@ export async function fetchWorkOrderById(workOrderId) {
 
 export async function fetchWorkOrderTaskServiceContext(workOrderId) {
     if (!workOrderId) {
-        return { tasks: [] };
+        return { tasks: [], additional_costs_table: null };
     }
     const payload = await api.get(`fleet/work-orders/${encodeURIComponent(workOrderId)}/task-service-context/`);
-    return payload && typeof payload === 'object' ? payload : { tasks: [] };
+    return payload && typeof payload === 'object' ? payload : { tasks: [], additional_costs_table: null };
+}
+
+export async function fetchWorkOrderAdditionalCostsTable(workOrderId) {
+    if (!workOrderId) {
+        return { data: { rows: [] }, total_for_payout: '0.00' };
+    }
+    const payload = await api.get(`fleet/work-orders/${encodeURIComponent(workOrderId)}/additional-costs-table/`);
+    return payload && typeof payload === 'object'
+        ? payload
+        : { data: { rows: [] }, total_for_payout: '0.00' };
+}
+
+export async function updateWorkOrderAdditionalCostsTable(workOrderId, data) {
+    if (!workOrderId) {
+        throw new Error('Work order ID je obavezan.');
+    }
+    const payload = await api.put(
+        `fleet/work-orders/${encodeURIComponent(workOrderId)}/additional-costs-table/`,
+        data ?? { rows: [] },
+    );
+    showToast('Dodatni troškovi su uspješno spremljeni.', 'success');
+    return payload;
 }
 
 export async function updateTaskWorkHoursTable(taskId, data) {