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/data/state/runtime.rs

@@ -22,6 +22,7 @@ use super::{
     VideoTaskModelCount, VideoTaskQueryFilter, VideoTaskStatusCount, WalletLookupKey,
     WalletMutationOutcome,
 };
+use aether_data_contracts::repository::usage::UsageAuditListQuery;
 use aether_video_tasks_core::read_data_backed_video_task_response;
 
 fn is_missing_shadow_results_relation_error(error: &DataLayerError) -> bool {
@@ -640,7 +641,7 @@ impl GatewayDataState {
 
     pub(crate) async fn list_usage_audits(
         &self,
-        query: &aether_data::repository::usage::UsageAuditListQuery,
+        query: &UsageAuditListQuery,
     ) -> Result<Vec<StoredRequestUsageAudit>, DataLayerError> {
         match &self.usage_reader {
             Some(repository) => repository.list_usage_audits(query).await,