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>

lib/features/editor/document_save_action.dart

@@ -0,0 +1,53 @@
+import '../../models/document_model.dart';
+
+enum DocumentSaveActionKind { putExisting, reuploadThenPut, blocked }
+
+/// Decides how an editor's save flow should reach the server, given whether
+/// a real server-assigned document is already resolved. Deliberately
+/// separated from the Dio call sites (`editor_screen.dart`,
+/// `product_editor_logic.dart`) so the guard against PUTting to a
+/// fabricated client-side ID - a millisecond timestamp that can never match
+/// the int4 `documents.id` (gap G5, `docs/api-contract-map.md`) - is
+/// unit-testable without mocking network I/O, mirroring the pure-decision
+/// pattern used by `poll_outcome.dart` (task 6.1).
+class DocumentSaveAction {
+  final DocumentSaveActionKind kind;
+  final String? serverId;
+  final String? blockedMessage;
+
+  const DocumentSaveAction._(this.kind, {this.serverId, this.blockedMessage});
+
+  factory DocumentSaveAction.putExisting(String serverId) =>
+      DocumentSaveAction._(DocumentSaveActionKind.putExisting, serverId: serverId);
+
+  factory DocumentSaveAction.reuploadThenPut() =>
+      const DocumentSaveAction._(DocumentSaveActionKind.reuploadThenPut);
+
+  factory DocumentSaveAction.blocked(String message) =>
+      DocumentSaveAction._(DocumentSaveActionKind.blocked, blockedMessage: message);
+}
+
+/// [existingDocument] is the server document already resolved from a
+/// completed upload+parse (e.g. `PendingDocument.document`) - when present,
+/// its real id is used for the PUT. When absent (e.g. the editor route lost
+/// its `pendingId` on process-death restoration), [localImagePath] - the
+/// pending item's originally-captured photo - lets the save flow recover a
+/// real server id by re-uploading it (safe: the backend dedups by
+/// `file_hash`) before PUTting the corrected fields. If neither is
+/// available there is nothing to save against, so saving is blocked with an
+/// explicit message instead of PUTting to a made-up ID that can never match
+/// a real document.
+DocumentSaveAction resolveDocumentSaveAction({
+  required DocumentModel? existingDocument,
+  required String localImagePath,
+}) {
+  if (existingDocument != null) {
+    return DocumentSaveAction.putExisting(existingDocument.id);
+  }
+  if (localImagePath.isEmpty) {
+    return DocumentSaveAction.blocked(
+      'Tidak dapat menyimpan: dokumen asli tidak ditemukan di perangkat. Silakan pindai ulang.',
+    );
+  }
+  return DocumentSaveAction.reuploadThenPut();
+}