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/internal/gateway_helpers.rs

@@ -12,7 +12,7 @@ use crate::execution_runtime::{
     maybe_build_local_video_success_outcome, resolve_local_sync_error_background_report_kind,
     resolve_local_sync_success_background_report_kind,
 };
-use crate::handlers::admin::provider::oauth::build_internal_control_error_response;
+use crate::handlers::admin::provider::oauth::refresh::build_internal_control_error_response;
 use crate::handlers::shared::{
     unix_secs_to_rfc3339, InternalTunnelHeartbeatRequest, InternalTunnelNodeStatusRequest,
 };

apps/aether-gateway/src/handlers/internal/mod.rs

@@ -1,4 +1,4 @@
-use super::admin::provider::oauth::build_internal_control_error_response;
+use super::admin::provider::oauth::refresh::build_internal_control_error_response;
 
 mod gateway_helpers;
 use self::gateway_helpers::*;