refactor: 提取搜索逻辑到 Model Scope

- User: 新增 scopeSearchByKeyword
  - Project: 新增 scopeSearchByKeyword
  - ProjectTask: 新增 scopeSearchByKeyword
  - File: 新增 scopeSearchByKeyword, scopeSharedToUser
  - WebSocketDialogMsg: 新增 scopeSearchByKeyword, scopeAccessibleByUser
  - SearchController: 使用新的 Model Scope 简化 MySQL 回退逻辑

app/Models/Project.php

@@ -164,6 +164,18 @@ class Project extends AbstractModel
         return $query;
     }
 
+    /**
+     * 按关键词搜索项目（Scope）
+     *
+     * @param \Illuminate\Database\Eloquent\Builder $query
+     * @param string $keyword 搜索关键词
+     * @return \Illuminate\Database\Eloquent\Builder
+     */
+    public function scopeSearchByKeyword($query, string $keyword)
+    {
+        return $query->where("projects.name", "like", "%{$keyword}%");
+    }
+
     /**
      * 获取任务统计数据
      * @param $userid