perf: Q3 N+1 查询优化 — user_service 和 plugin_service

- user_service::list() 循环内单查询改为 fetch_batch_user_role_resps 批量查询
- plugin_service::list() 循环内单查询改为 find_batch_plugin_entities 批量查询
- RoleResp 和 PluginEntityResp 添加 Clone derive

crates/erp-plugin/src/dto.rs

@@ -25,7 +25,7 @@ pub struct PluginResp {
 }
 
 /// 插件实体信息
-#[derive(Debug, Serialize, Deserialize, utoipa::ToSchema)]
+#[derive(Debug, Clone, Serialize, Deserialize, utoipa::ToSchema)]
 pub struct PluginEntityResp {
     pub name: String,
     pub display_name: String,