feat(app): P0 batch 2+2.5 — local upload dedup with batch dialog, album switch check, file size guard

P0-1 层 1 本地查重：
  - checkDuplicates：同账号+同相册+state=completed+filename+bytes 匹配
  - EnqueueResult 返回 enqueued+duplicates+skipped
  - capture_page + album_detail_page：批量单次弹窗（非逐张）三选一
    [跳过重复上传非重复] [全部上传] [取消]

P0-8 相册上传开关预检：album_detail_page 入队前检查 uploadEnabled，
  关闭时提示「该相册已关闭上传」+ 不入队

P1-8 文件大小预检：preparer 限单文件 ≤100MB（磁盘满由 on Object 兜底）

P0-7 更正：上传并发限制已有（kMaxParallelUploads=2），v2 分析误报

397/397 全绿、analyze 0

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

apps/mobile/lib/features/uploads/preparer.dart

@@ -55,8 +55,8 @@ class UploadPreparer {
     Random? random,
     this.maxBytes = kMaxUploadBytes,
     this.onEnqueued,
-  })  : _baseDirProvider = baseDirProvider ?? getApplicationSupportDirectory,
-        _random = random ?? Random.secure();
+  }) : _baseDirProvider = baseDirProvider ?? getApplicationSupportDirectory,
+       _random = random ?? Random.secure();
 
   final TaskStore _store;
   final Future<Directory> Function() _baseDirProvider;
@@ -88,13 +88,15 @@ class UploadPreparer {
     required String sourcePath,
     String? filename,
   }) {
-    return _serialize(() => _prepare(
-          accountId: accountId,
-          albumId: albumId,
-          categoryId: categoryId,
-          sourcePath: sourcePath,
-          filename: filename,
-        ));
+    return _serialize(
+      () => _prepare(
+        accountId: accountId,
+        albumId: albumId,
+        categoryId: categoryId,
+        sourcePath: sourcePath,
+        filename: filename,
+      ),
+    );
   }
 
   /// 重试准备失败的任务（preparationFailed → preparing → 复制 → queued）。
@@ -106,11 +108,10 @@ class UploadPreparer {
     required String taskId,
     required String sourcePath,
   }) {
-    return _serialize(() => _retry(
-          accountId: accountId,
-          taskId: taskId,
-          sourcePath: sourcePath,
-        ));
+    return _serialize(
+      () =>
+          _retry(accountId: accountId, taskId: taskId, sourcePath: sourcePath),
+    );
   }
 
   /// 串行化：所有准备操作首尾相接（错误吞掉以不断链，错误经返回值上抛）。
@@ -196,6 +197,11 @@ class UploadPreparer {
       if (expected <= 0) {
         throw StateError('empty source');
       }
+      // P1-8：磁盘空间预检——超 100MB 直接拒绝（copy 阶段的磁盘满错误
+      // 已被下方 on Object 兜底为 copyFailed；此上限防止单文件打满存储）。
+      if (expected > 100 * 1024 * 1024) {
+        throw StateError('source too large');
+      }
       await target.parent.create(recursive: true);
       await source.copy(task.sourceFilePath);
       final copied = await target.length();