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

crates/aether-usage-runtime/src/worker.rs

@@ -2,8 +2,8 @@ use std::sync::Arc;
 use std::time::Duration;
 
 use aether_data::redis::{RedisConsumerName, RedisStreamEntry, RedisStreamRunner};
-use aether_data::repository::usage::{StoredRequestUsageAudit, UpsertUsageRecord};
-use aether_data::DataLayerError;
+use aether_data_contracts::repository::usage::{StoredRequestUsageAudit, UpsertUsageRecord};
+use aether_data_contracts::DataLayerError;
 use async_trait::async_trait;
 use tracing::warn;
 
@@ -226,8 +226,10 @@ fn consumer_name() -> String {
 mod tests {
     use std::sync::Mutex;
 
-    use aether_data::repository::settlement::{StoredUsageSettlement, UsageSettlementInput};
-    use aether_data::repository::usage::{StoredRequestUsageAudit, UpsertUsageRecord};
+    use aether_data_contracts::repository::settlement::{
+        StoredUsageSettlement, UsageSettlementInput,
+    };
+    use aether_data_contracts::repository::usage::{StoredRequestUsageAudit, UpsertUsageRecord};
     use async_trait::async_trait;
 
     use super::{write_event_record, UsageRecordWriter};
@@ -244,7 +246,8 @@ mod tests {
         async fn upsert_usage_record(
             &self,
             record: UpsertUsageRecord,
-        ) -> Result<Option<StoredRequestUsageAudit>, aether_data::DataLayerError> {
+        ) -> Result<Option<StoredRequestUsageAudit>, aether_data_contracts::DataLayerError>
+        {
             self.records
                 .lock()
                 .expect("records lock")
@@ -304,7 +307,7 @@ mod tests {
         async fn settle_usage(
             &self,
             input: UsageSettlementInput,
-        ) -> Result<Option<StoredUsageSettlement>, aether_data::DataLayerError> {
+        ) -> Result<Option<StoredUsageSettlement>, aether_data_contracts::DataLayerError> {
             self.settlements
                 .lock()
                 .expect("settlements lock")