业务更新User所需（企业成员、聊天室群组成员）

apps/im_app/lib/features/chat/usecases/delete_users_use_case.dart

@@ -0,0 +1,39 @@
+import 'package:im_app/domain/entities/user.dart';
+import 'package:im_app/domain/repositories/user_repository.dart';
+
+/// 删除前10个用户用例
+///
+/// ## 职责
+/// - 取前10个用户
+/// - 按 uid 逐条删除
+///
+/// ## 数据流
+/// ```
+/// ViewModel
+///   → DeleteUsersUseCase.execute(users)
+///     → 取前10条
+///     → UserRepository.deleteUser(uid) × n
+///   ← 已删除的用户列表
+/// ```
+class DeleteUsersUseCase {
+  final UserRepository _repo;
+
+  DeleteUsersUseCase({required UserRepository userRepository})
+    : _repo = userRepository;
+
+  /// 删除前10个用户
+  ///
+  /// [users] 当前用户列表，取前10条删除
+  /// 返回已删除的用户列表，供 ViewModel 从 UI 中移除
+  Future<List<User>> execute(List<User> users) async {
+    if (users.isEmpty) return [];
+
+    final targets = users.take(10).toList();
+
+    for (final user in targets) {
+      await _repo.deleteUser(user.uid);
+    }
+
+    return targets;
+  }
+}

apps/im_app/lib/features/chat/usecases/insert_users_use_case.dart

@@ -44,7 +44,7 @@ class InsertUsersUseCase {
       final end = (completed + _chunkSize).clamp(0, total);
       final chunk = deduped.sublist(completed, end);
 
-      await _repo.saveUsers(chunk);
+      await _repo.insertOrReplaceUsers(chunk);
       completed += chunk.length;
 
       onProgress?.call(completed, total, chunk);

apps/im_app/lib/features/chat/usecases/update_users_use_case.dart

@@ -0,0 +1,53 @@
+import 'dart:math';
+
+import 'package:im_app/domain/entities/user.dart';
+import 'package:im_app/domain/repositories/user_repository.dart';
+
+/// 更新前10个用户名称用例
+///
+/// ## 职责
+/// - 取前10个用户
+/// - 随机生成新昵称（6位随机字母 + uid）
+/// - 批量更新到 DB
+///
+/// ## 数据流
+/// ```
+/// ViewModel
+///   → UpdateUsersUseCase.execute(users)
+///     → 取前10条
+///     → 随机生成昵称
+///     → UserRepository.updateUsersBatch(targets)
+///   ← 更新后的用户列表
+/// ```
+class UpdateUsersUseCase {
+  final UserRepository _repo;
+  final _random = Random();
+
+  UpdateUsersUseCase({required UserRepository userRepository})
+    : _repo = userRepository;
+
+  String _randomWord() {
+    const letters = 'abcdefghijklmnopqrstuvwxyz';
+    return List.generate(
+      6,
+      (_) => letters[_random.nextInt(letters.length)],
+    ).join();
+  }
+
+  /// 更新前10个用户的昵称
+  ///
+  /// [users] 当前用户列表，取前10条更新
+  /// 返回更新后的前10个用户，供 ViewModel 直接反映到 UI
+  Future<List<User>> execute(List<User> users) async {
+    if (users.isEmpty) return [];
+
+    final targets = users
+        .take(10)
+        .map((u) => u.copyWith(nickname: '${_randomWord()}_${u.uid}'))
+        .toList();
+
+    await _repo.updateUsersBatch(targets);
+
+    return targets;
+  }
+}