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/pages/capture_page.dart

@@ -462,13 +462,16 @@ class _CapturePageState extends ConsumerState<CapturePage>
     );
 
     Set<String> skipPaths;
+    Set<String> forcePaths;
     if (duplicates != null && duplicates.isNotEmpty && mounted) {
       // 批量确认弹窗（单次，非逐张）。
-      final skip = await _showDuplicateDialog(l10n, duplicates, paths);
-      if (skip == null) return; // 取消——不上传。
-      skipPaths = skip;
+      final choice = await _showDuplicateDialog(l10n, duplicates, paths);
+      if (choice == null) return; // 取消——不上传。
+      skipPaths = choice.skipPaths;
+      forcePaths = choice.forcePaths;
     } else {
       skipPaths = <String>{};
+      forcePaths = <String>{};
     }
 
     final result = await enqueueForUpload(
@@ -478,6 +481,7 @@ class _CapturePageState extends ConsumerState<CapturePage>
       categoryId: _categoryId,
       sourcePaths: paths,
       skipPaths: skipPaths.toList(),
+      forcePaths: forcePaths.toList(),
     );
     if (!mounted) return;
     final uploaded = result.enqueued;
@@ -493,8 +497,10 @@ class _CapturePageState extends ConsumerState<CapturePage>
     );
   }
 
-  /// 批量重复确认弹窗：返回 null=取消 / 空 Set=全部上传 / 非空=跳过项路径集。
-  Future<Set<String>?> _showDuplicateDialog(
+  /// 批量重复确认弹窗（Task 8）：null=取消；「跳过重复」→ skipPaths=
+  /// 重复项；「全部上传」→ forcePaths=重复项（用户确认强传，服务端
+  /// force 查重跳过仅 owner/admin 生效——协作者仍会被 409 拒绝）。
+  Future<DuplicateDialogChoice?> _showDuplicateDialog(
     AppLocalizations l10n,
     List<DuplicateMatch> duplicates,
     List<String> allPaths,
@@ -535,8 +541,11 @@ class _CapturePageState extends ConsumerState<CapturePage>
     );
 
     if (choice == 'cancel' || choice == null) return null;
-    if (choice == 'skip') return dupPaths;
-    return <String>{}; // 'all' = 不跳过任何
+    if (choice == 'skip') {
+      return (skipPaths: dupPaths, forcePaths: <String>{});
+    }
+    // 'all' = 用户确认强传：重复项 force 入队（不跳过任何）。
+    return (skipPaths: <String>{}, forcePaths: dupPaths);
   }
 
   void _switchCategory(String? categoryId) {