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/model/write.rs

@@ -2,8 +2,8 @@ use super::payloads::{normalize_optional_price, normalize_required_trimmed_strin
 use crate::handlers::admin::model::shared::{
     AdminGlobalModelCreateRequest, AdminGlobalModelUpdateRequest,
 };
+use crate::handlers::admin::request::AdminAppState;
 use crate::handlers::admin::shared::{normalize_json_object, normalize_string_list};
-use crate::AppState;
 use aether_data_contracts::repository::global_models::{
     CreateAdminGlobalModelRecord, StoredAdminGlobalModel, UpdateAdminGlobalModelRecord,
 };
@@ -11,7 +11,7 @@ use serde_json::json;
 use uuid::Uuid;
 
 pub(crate) async fn build_admin_global_model_create_record(
-    state: &AppState,
+    state: &AdminAppState<'_>,
     payload: AdminGlobalModelCreateRequest,
 ) -> Result<CreateAdminGlobalModelRecord, String> {
     let name = normalize_required_trimmed_string(&payload.name, "name")?;
@@ -47,7 +47,7 @@ pub(crate) async fn build_admin_global_model_create_record(
 }
 
 pub(crate) async fn build_admin_global_model_update_record(
-    _state: &AppState,
+    _state: &AdminAppState<'_>,
     existing: &StoredAdminGlobalModel,
     raw_payload: &serde_json::Map<String, serde_json::Value>,
     payload: AdminGlobalModelUpdateRequest,