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/provider_query.rs

@@ -1,9 +1,8 @@
 use std::sync::{Arc, Mutex};
 
 use aether_data::repository::global_models::InMemoryGlobalModelReadRepository;
-use aether_data::repository::provider_catalog::{
-    InMemoryProviderCatalogReadRepository, StoredProviderCatalogEndpoint,
-};
+use aether_data::repository::provider_catalog::InMemoryProviderCatalogReadRepository;
+use aether_data_contracts::repository::provider_catalog::StoredProviderCatalogEndpoint;
 use axum::body::Body;
 use axum::routing::any;
 use axum::{extract::Request, Router};
@@ -248,6 +247,27 @@ async fn gateway_handles_admin_provider_query_test_model_failover_locally_with_t
     .await;
 }
 
+#[tokio::test]
+async fn gateway_handles_admin_provider_query_test_model_failover_with_single_model_name_alias() {
+    assert_admin_provider_query_route(
+        "/api/admin/provider-query/test-model-failover",
+        json!({
+            "provider_id": "provider-openai",
+            "model_name": "gpt-4.1"
+        }),
+        StatusCode::OK,
+        |payload| {
+            assert_eq!(payload["success"], json!(false));
+            assert_eq!(payload["tested"], json!(false));
+            assert_eq!(payload["model"], json!("gpt-4.1"));
+            assert_eq!(payload["failover_models"], json!(["gpt-4.1"]));
+            assert_eq!(payload["attempts"], json!([]));
+            assert_eq!(payload["total_attempts"], json!(0));
+        },
+    )
+    .await;
+}
+
 #[tokio::test]
 async fn gateway_rejects_admin_provider_query_invalid_json_body() {
     let upstream_hits = Arc::new(Mutex::new(0usize));