持久化 provider key 使用统计并移除 usage 汇总覆盖 (#313)

* 持久化 provider key 使用统计并移除 usage 汇总覆盖

- 在 usage upsert 时按请求前后差值同步 provider_api_keys 统计
- 增加基于保留 usage 记录的 provider key 统计重建能力
- 号池管理列表直接读取 provider_api_keys 统计字段

* fix: harden provider key usage stats sync

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Co-authored-by: fawney19 <elky0401@gmail.com>

crates/aether-data-contracts/src/repository/usage/types.rs

@@ -1539,6 +1539,8 @@ pub trait UsageWriteRepository: Send + Sync {
         &self,
         usage: UpsertUsageRecord,
     ) -> Result<StoredRequestUsageAudit, crate::DataLayerError>;
+
+    async fn rebuild_provider_api_key_usage_stats(&self) -> Result<u64, crate::DataLayerError>;
 }
 
 pub trait UsageRepository: UsageReadRepository + UsageWriteRepository + Send + Sync {}