refactor: 拆分 admin handler 大文件为模块目录，消除 shared.rs 反模式

- endpoint_keys/pool/architecture 等大文件拆分为独立模块目录
- 删除 crud/query/strategy/system 中的 shared.rs，内容归位到各自模块
- endpoints_admin/models/oauth/write 等模块拆出 payloads/responses/support 子文件
- system/core 下多个 *_routes.rs 合并到 system_routes.rs
- 更新 refactor-execution-plan 文档进度

apps/aether-gateway/src/maintenance/runtime.rs

@@ -16,7 +16,7 @@ use tracing::{debug, info, warn};
 use uuid::Uuid;
 
 use crate::data::GatewayDataState;
-use crate::handlers::admin::provider::ops::admin_provider_ops_local_action_response;
+use crate::handlers::admin::provider::ops::providers::actions::admin_provider_ops_local_action_response;
 use crate::{AppState, GatewayError};
 
 #[path = "runtime/audit_cleanup.rs"]

apps/aether-gateway/src/maintenance/runtime/provider_checkin.rs

@@ -6,7 +6,7 @@ use aether_data_contracts::repository::provider_catalog::{
 use futures_util::stream::{self, StreamExt};
 use tracing::{debug, warn};
 
-use crate::handlers::admin::provider::ops::admin_provider_ops_local_action_response;
+use crate::handlers::admin::provider::ops::providers::actions::admin_provider_ops_local_action_response;
 use crate::{AppState, GatewayError};
 
 use super::{system_config_bool, PROVIDER_CHECKIN_CONCURRENCY};