feat(app): scan-mode sync, confirmation-gated documents, single-pass product classification

Fixes reported from APK field testing: DO/Product scan mode was inconsistent
between the camera drawer and documents screen (now one shared provider,
with an orange/green color cue); unconfirmed scans leaked into history with
placeholder data before the user tapped confirm (backend now gates
GET /documents on a new `confirmed` column, flipped only by PUT); and
Product Scan ran the GPU classifier twice, once at upload and again on
review (now a single pass at upload, persisted and read directly by the
editor). Also removes the unused "Hubungkan ke PO" field and fabricated
PO/SO/DO placeholder values from the Product Scan flow, closes out the
per-document-polling and save-recovery tasks (6.1/6.3), and splits several
touched files to stay under the repo's 256-line guideline.

Full detail in docs/iteration-log.md and backend/docs/iteration-log.md.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

test/document_save_action_test.dart

@@ -0,0 +1,53 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:app_pfm_ocr_v2/features/editor/document_save_action.dart';
+import 'package:app_pfm_ocr_v2/models/document_model.dart';
+
+DocumentModel _doc(String id) {
+  return DocumentModel(
+    id: id,
+    tanggal: '',
+    noPo: '',
+    noSo: '',
+    noDo: '',
+    kepadaYth: '',
+    orderUntuk: '',
+    alamat: '',
+    platTruk: '',
+    namaDriver: '',
+    namaPenerima: '',
+    items: const [],
+    createdAt: DateTime(2026, 7, 10),
+  );
+}
+
+void main() {
+  group('resolveDocumentSaveAction', () {
+    test('a resolved server document -> putExisting with its real id', () {
+      final action = resolveDocumentSaveAction(
+        existingDocument: _doc('3390'),
+        localImagePath: '/tmp/photo.jpg',
+      );
+      expect(action.kind, DocumentSaveActionKind.putExisting);
+      expect(action.serverId, '3390');
+    });
+
+    test('no resolved document but a local image is available -> reuploadThenPut, never a fabricated id', () {
+      final action = resolveDocumentSaveAction(
+        existingDocument: null,
+        localImagePath: '/tmp/photo.jpg',
+      );
+      expect(action.kind, DocumentSaveActionKind.reuploadThenPut);
+      expect(action.serverId, isNull);
+    });
+
+    test('no resolved document and no local image -> blocked with an explicit message', () {
+      final action = resolveDocumentSaveAction(
+        existingDocument: null,
+        localImagePath: '',
+      );
+      expect(action.kind, DocumentSaveActionKind.blocked);
+      expect(action.blockedMessage, isNotNull);
+      expect(action.blockedMessage, isNotEmpty);
+    });
+  });
+}