refactor: 大规模模块拆分与代码精简，新增 ai-pipeline/data-contracts 独立 crate

- 新增 aether-ai-pipeline 和 aether-data-contracts crate，将 pipeline 逻辑与数据契约从 gateway 中解耦
- 重构 admin handlers：拆分单体模块为 auth/billing/endpoint/features/model/observability/provider/system 等独立子模块
- 合并 chat/cli 重复代码路径：精简 conversion、finalize、planner 中的 sync/chat/cli 分支
- 重构 scheduler/executor/data 层，引入 facade 模式降低模块间耦合
- 移除冗余的 intent 模块，将 plan_fallback/policy/stream_path/sync_path 迁移至 executor
- 前端适配：调整 admin API 调用和 provider 模型测试对话框

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

@@ -0,0 +1,50 @@
+use super::super::users::{
+    default_admin_user_api_key_name, format_optional_unix_secs_iso8601,
+    generate_admin_user_api_key_plaintext, hash_admin_user_api_key, masked_user_api_key_display,
+    normalize_admin_optional_api_key_name, normalize_admin_user_api_formats,
+    normalize_admin_user_string_list,
+};
+use crate::control::GatewayPublicRequestContext;
+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::serialize_admin_system_users_export_wallet;
+use crate::{AppState, GatewayError};
+use axum::{
+    body::Body,
+    http,
+    response::{IntoResponse, Response},
+    Json,
+};
+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;
+mod shared;
+
+use self::mutation_routes::{
+    build_admin_create_api_key_response, build_admin_delete_api_key_response,
+    build_admin_toggle_api_key_response, build_admin_update_api_key_response,
+};
+use self::read_routes::{build_admin_api_key_detail_response, build_admin_list_api_keys_response};
+use self::shared::{
+    admin_api_key_total_tokens_by_ids, admin_api_keys_id_from_path, admin_api_keys_operator_id,
+    admin_api_keys_parse_limit, admin_api_keys_parse_skip, build_admin_api_key_detail_payload,
+    build_admin_api_key_list_item_payload, build_admin_api_keys_bad_request_response,
+    build_admin_api_keys_data_unavailable_response, build_admin_api_keys_not_found_response,
+    AdminStandaloneApiKeyCreateRequest, AdminStandaloneApiKeyFieldPresence,
+    AdminStandaloneApiKeyToggleRequest, AdminStandaloneApiKeyUpdateRequest,
+};
+
+pub(crate) async fn maybe_build_local_admin_api_keys_response(
+    state: &AppState,
+    request_context: &GatewayPublicRequestContext,
+    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)
+        .await
+}