feat(app): wire server dedup - force passthrough + PHOTO_DUPLICATE classification & l10n

Task 8: close the gap between server-side duplicate detection (90dcc58)
and the app.

- ApiClient.mapDioException: normalize 409 wire body reusing
  VALIDATION_FAILED with message=PHOTO_DUPLICATE to
  ErrorCodes.photoDuplicate (message-based; auto-compat if the contract
  later adds a dedicated code)
- l10n zh/en errorPhotoDuplicate; error_l10n maps the code (queue page
  inherits via fallback)
- UploadEngine._classifyFailure: PHOTO_DUPLICATE joins the no-auto-retry
  bucket (retrying the same init body would 409 again); force to skip
  dedup travels only through the enqueue path
- UploadTasks drift table +force column (schema v2, addColumn migration;
  legacy rows default false); UploadTaskDraft/UploadTask/prepare carry it
- enqueueForUpload +forcePaths; duplicate dialog "全部上传" (capture page
  + album detail page) now returns DuplicateDialogChoice so confirmed
  duplicates enqueue with force=true (server adjudicates owner/admin)
- engine init body carries force only when true (absent otherwise)

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

apps/mobile/lib/core/api_client.dart

@@ -137,6 +137,18 @@ class ApiClient {
         final Object? message = data['message'];
         final Object? requestId = data['requestId'];
         if (code is String && message is String) {
+          // P0-1 服务端查重拒绝（Task 8）：409 的 wire code 复用
+          // VALIDATION_FAILED，按 message=PHOTO_DUPLICATE 识别归一——所有
+          // 调用方（上传引擎分类/l10n 文案）据此走查重分支；契约日后若设
+          // 独立 code，此处识别与透传均兼容。
+          if (status == 409 && message.contains(ErrorCodes.photoDuplicate)) {
+            return AppException(
+              code: ErrorCodes.photoDuplicate,
+              message: message,
+              requestId: requestId is String ? requestId : null,
+              statusCode: status,
+            );
+          }
           return AppException(
             code: code,
             message: message,