feat: dodaj ishodište i PDF račune za putni nalog

Dodano je origin_location polje kroz backend model, serializer, admin i UI
modal za kreiranje/uređivanje putnog naloga (default: Zagreb).

Računi putnog naloga sada prihvaćaju slike i PDF datoteke, uz backend
validaciju formata, podršku za serving PDF-a i prilagodbu preview prikaza.

Za greške uploada računa dodan je error toast kako bi poruke validacije bile
vidljive korisniku odmah u sučelju.

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

backend/modules/fleet/migrations/0027_workorder_origin_location.py

@@ -0,0 +1,16 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('fleet', '0026_backfill_workorder_display_code'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='workorder',
+            name='origin_location',
+            field=models.CharField(blank=True, max_length=255, verbose_name='Lokacija ishodišta'),
+        ),
+    ]

backend/modules/fleet/migrations/0028_alter_workorderinvoice_image.py

@@ -0,0 +1,18 @@
+from django.db import migrations, models
+
+import modules.fleet.models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('fleet', '0027_workorder_origin_location'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='workorderinvoice',
+            name='image',
+            field=models.FileField(blank=True, null=True, upload_to=modules.fleet.models._work_order_invoice_upload_to, verbose_name='Datoteka računa'),
+        ),
+    ]