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/handlers/admin/provider/ops/mod.rs

@@ -4,9 +4,7 @@ use axum::body::{Body, Bytes};
 use axum::http::Response;
 
 mod architectures;
-mod providers;
-
-pub(crate) use self::providers::admin_provider_ops_local_action_response;
+pub(crate) mod providers;
 
 pub(crate) async fn maybe_build_local_admin_provider_ops_response(
     state: &AppState,