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/tests/control/admin/system.rs

@@ -9,15 +9,13 @@ use aether_data::repository::auth_modules::{
     InMemoryAuthModuleReadRepository, StoredOAuthProviderModuleConfig,
 };
 use aether_data::repository::candidates::InMemoryRequestCandidateRepository;
-use aether_data::repository::global_models::{
-    InMemoryGlobalModelReadRepository, StoredPublicGlobalModel,
-};
+use aether_data::repository::global_models::InMemoryGlobalModelReadRepository;
 use aether_data::repository::oauth_providers::InMemoryOAuthProviderRepository;
 use aether_data::repository::provider_catalog::InMemoryProviderCatalogReadRepository;
 use aether_data::repository::proxy_nodes::InMemoryProxyNodeRepository;
 use aether_data::repository::users::{InMemoryUserReadRepository, StoredUserExportRow};
-use aether_data::repository::wallet::InMemoryWalletRepository;
-use aether_data::repository::wallet::StoredWalletSnapshot;
+use aether_data::repository::wallet::{InMemoryWalletRepository, StoredWalletSnapshot};
+use aether_data_contracts::repository::global_models::StoredPublicGlobalModel;
 use axum::body::Body;
 use axum::routing::{any, delete, get, post, put};
 use axum::{extract::Request, Router};