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/features/uploads/preparer_test.dart

@@ -124,6 +124,26 @@ void main() {
       await p.prepare(accountId: 'alice', albumId: 'alb-1', sourcePath: src.path);
       expect(enqueued, 1);
     });
+
+    test('force 透传（Task 8）：缺省 false，force=true 落到任务行', () async {
+      final src = sourceFile('force.jpg', _jpgBytes);
+      final p = preparer();
+
+      final normal = await p.prepare(
+        accountId: 'alice',
+        albumId: 'alb-1',
+        sourcePath: src.path,
+      );
+      expect(normal.force, isFalse, reason: '缺省不强传');
+
+      final forced = await p.prepare(
+        accountId: 'alice',
+        albumId: 'alb-1',
+        sourcePath: src.path,
+        force: true,
+      );
+      expect(forced.force, isTrue, reason: '弹窗「全部上传」的强传标记落库');
+    });
   });
 
   group('prepare（预检失败 → preparationFailed）', () {