refactor: 大规模模块拆分与重组，新增 aether-admin crate

- 新建独立 aether-admin crate 承载 admin 相关共享契约与纯辅助函数
- 拆分 ai_pipeline 下 kiro/private_envelope/conversion/planner 等大文件为子模块目录
- 重组 admin handlers 各业务域（billing/oauth/provider/system/users 等）为目录结构，移除 shared.rs/builders.rs 等反模式
- 移除 ai_pipeline runtime adapters 旧实现（claude/openai/gemini/kiro/vertex/antigravity 等），改由 provider transport 统一承载
- 移除 control_facade/execution_facade/auth_snapshot_facade 等冗余 facade 层
- 拆分 query/billing 与 query/monitoring 模块、state/runtime/payments 与 security 模块
- 扩展架构测试覆盖 admin_billing/admin_model/admin_users 等新模块
- 删除 docs/architecture/refactor-execution-plan.md 已完成的执行计划文档

apps/aether-gateway/src/handlers/admin/auth/api_keys/mod.rs

@@ -4,13 +4,12 @@ use super::super::users::{
     normalize_admin_optional_api_key_name, normalize_admin_user_api_formats,
     normalize_admin_user_string_list,
 };
-use crate::control::GatewayPublicRequestContext;
+use crate::handlers::admin::request::{AdminAppState, AdminRequestContext};
 use crate::handlers::admin::shared::{
     decrypt_catalog_secret_with_fallbacks, encrypt_catalog_secret_with_fallbacks, query_param_bool,
     query_param_optional_bool, query_param_value,
 };
-use crate::handlers::admin::system::shared::configs::serialize_admin_system_users_export_wallet;
-use crate::{AppState, GatewayError};
+use crate::GatewayError;
 use axum::{
     body::Body,
     http,
@@ -19,8 +18,6 @@ use axum::{
 };
 use serde_json::json;
 
-const ADMIN_API_KEYS_DATA_UNAVAILABLE_DETAIL: &str = "Admin standalone API key data unavailable";
-
 mod mutation_routes;
 mod read_routes;
 mod routes;
@@ -41,8 +38,8 @@ use self::shared::{
 };
 
 pub(crate) async fn maybe_build_local_admin_api_keys_response(
-    state: &AppState,
-    request_context: &GatewayPublicRequestContext,
+    state: &AdminAppState<'_>,
+    request_context: &AdminRequestContext<'_>,
     request_body: Option<&axum::body::Bytes>,
 ) -> Result<Option<Response<Body>>, GatewayError> {
     routes::maybe_build_local_admin_api_keys_routes_response(state, request_context, request_body)