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/tests/control/admin/provider_ops.rs

@@ -947,8 +947,8 @@ async fn gateway_verifies_admin_provider_ops_locally_for_anyrouter_proxy_mode()
         .and_then(serde_json::Value::as_str)
         .unwrap_or_default();
     assert!(
-        message.starts_with("连接失败:"),
-        "message should include connect error, got: {message}"
+        message.starts_with("连接失败:") || message == "连接超时",
+        "message should report local network verification failure, got: {message}"
     );
     assert_eq!(*upstream_hits.lock().expect("mutex should lock"), 0);