feat: 引入 CloudSync 核心能力并新增 Avalonia 桌面端与发布脚本

- 后端：新增 CloudSync 认证/权限/端点/服务与 DTO
- 数据：新增用户/会话/安全策略实体与 EF Core migrations
- 前端：新增云同步设置 UI、客户端与本地存储；Vite 支持 maui 构建输出到 wwwroot
- 桌面端：新增 Avalonia 项目、内置 WebServer、托盘与 Windows 全局热键
- 发布/构建：新增 Windows/Linux 发布脚本与统一入口；调整 MAUI 资源与安装包配置
- 文档：同步更新 README/docs 与协作规则

src/Hua.Todo.Application/Repositories/TaskRepository.cs

@@ -28,6 +28,7 @@ public class TaskRepository : ITaskRepository
     public async Task<List<TaskEntity>> GetAllAsync()
     {
         return await _context.Tasks
+            .Where(t => t.UserId == TodoUserIds.LocalUserId)
             .Include(t => t.SubTasks)
             .ToListAsync();
     }
@@ -41,7 +42,7 @@ public class TaskRepository : ITaskRepository
     {
         return await _context.Tasks
             .Include(t => t.SubTasks)
-            .FirstOrDefaultAsync(t => t.Id == id);
+            .FirstOrDefaultAsync(t => t.Id == id && t.UserId == TodoUserIds.LocalUserId);
     }
 
     /// <summary>
@@ -51,7 +52,7 @@ public class TaskRepository : ITaskRepository
     public async Task<List<TaskEntity>> GetActiveTasksAsync()
     {
         return await _context.Tasks
-            .Where(t => !t.IsCompleted)
+            .Where(t => t.UserId == TodoUserIds.LocalUserId && !t.IsCompleted)
             .OrderByDescending(t => t.CreatedAt)
             .ToListAsync();
     }
@@ -63,7 +64,7 @@ public class TaskRepository : ITaskRepository
     public async Task<List<TaskEntity>> GetCompletedTasksAsync()
     {
         return await _context.Tasks
-            .Where(t => t.IsCompleted)
+            .Where(t => t.UserId == TodoUserIds.LocalUserId && t.IsCompleted)
             .OrderByDescending(t => t.UpdatedAt)
             .ToListAsync();
     }
@@ -75,6 +76,7 @@ public class TaskRepository : ITaskRepository
     /// <returns>已持久化的任务实体（包含生成的 ID）。</returns>
     public async Task<TaskEntity> AddAsync(TaskEntity taskEntity)
     {
+        taskEntity.UserId = TodoUserIds.LocalUserId;
         _context.Tasks.Add(taskEntity);
         await _context.SaveChangesAsync();
         return taskEntity;
@@ -100,7 +102,7 @@ public class TaskRepository : ITaskRepository
     /// <returns>表示删除操作的任务。</returns>
     public async Task DeleteAsync(int id)
     {
-        var task = await _context.Tasks.FindAsync(id);
+        var task = await _context.Tasks.FirstOrDefaultAsync(t => t.Id == id && t.UserId == TodoUserIds.LocalUserId);
         if (task != null)
         {
             _context.Tasks.Remove(task);
@@ -116,7 +118,7 @@ public class TaskRepository : ITaskRepository
     public async Task<List<TaskEntity>> GetSubTasksAsync(int parentTaskId)
     {
         return await _context.Tasks
-            .Where(t => t.ParentTaskId == parentTaskId)
+            .Where(t => t.UserId == TodoUserIds.LocalUserId && t.ParentTaskId == parentTaskId)
             .OrderByDescending(t => t.CreatedAt)
             .ToListAsync();
     }