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/test/core/error_codes_test.dart

@@ -106,6 +106,50 @@ void main() {
     });
   });
 
+  group('mapDioException：P0-1 服务端查重 409 归一（Task 8）', () {
+    test('409 VALIDATION_FAILED + message PHOTO_DUPLICATE → 归一为 PHOTO_DUPLICATE', () {
+      final ex = ApiClient.mapDioException(_httpError(409, {
+        'code': ErrorCodes.validationFailed,
+        'message': 'PHOTO_DUPLICATE',
+        'requestId': 'req-dup',
+      }));
+      expect(ex.code, ErrorCodes.photoDuplicate);
+      expect(ex.statusCode, 409);
+      expect(ex.requestId, 'req-dup', reason: '诊断字段保留');
+    });
+
+    test('契约日后设独立 code=PHOTO_DUPLICATE → 原样透传（归一兼容演进）', () {
+      final ex = ApiClient.mapDioException(_httpError(409, {
+        'code': ErrorCodes.photoDuplicate,
+        'message': 'duplicate photo',
+        'requestId': 'r',
+      }));
+      expect(ex.code, ErrorCodes.photoDuplicate);
+      expect(ex.statusCode, 409);
+    });
+
+    test('非查重语义不受归一影响（同 code 不同 message / 非 409）', () {
+      // 409 VALIDATION_FAILED 但 message 不是查重（如幂等参数校验）。
+      expect(
+        ApiClient.mapDioException(_httpError(409, {
+          'code': ErrorCodes.validationFailed,
+          'message': 'bytes out of range',
+          'requestId': 'r',
+        })).code,
+        ErrorCodes.validationFailed,
+      );
+      // 400 VALIDATION_FAILED 是普通校验失败（非查重拒绝路径）。
+      expect(
+        ApiClient.mapDioException(_httpError(400, {
+          'code': ErrorCodes.validationFailed,
+          'message': 'PHOTO_DUPLICATE',
+          'requestId': 'r',
+        })).code,
+        ErrorCodes.validationFailed,
+      );
+    });
+  });
+
   group('mapDioException：网络层（客户端伪码）', () {
     test('连接失败 → NETWORK_ERROR', () {
       final ex = ApiClient.mapDioException(