feat(gateway/data): 新增 usage 关键词搜索、缓存命中摘要、结算成本摘要及 dashboard 聚合查询能力

- 新增 UsageAuditKeywordSearchQuery，支持多关键词、用户名、API Key 交叉过滤
- 新增 UsageCacheHitSummaryQuery/StoredUsageCacheHitSummary，统计请求缓存命中率
- 新增 UsageSettledCostSummaryQuery/StoredUsageSettledCostSummary，汇总结算成本
- 新增 UsageDashboardSummaryQuery、UsageBreakdownSummaryQuery 等 dashboard 聚合类型
- SQL 层实现对应查询方法，含 list_by_ids、list_usage_audits_by_keyword_search、count_usage_audits_by_keyword_search
- 将上述能力通过 GatewayDataState / AdminAppState 暴露给 handler 层
- user_me_usage 及 dashboard_filters 切换为新查询接口，移除旧的内存过滤逻辑
- 同步更新 memory 层及测试

apps/aether-gateway/src/admin_api.rs

@@ -7,7 +7,6 @@ pub(crate) use crate::handlers::admin::{
 
 use crate::handlers::admin::{
     admin_stats_bad_request_response as admin_stats_bad_request_response_impl,
-    list_usage_for_optional_range as list_usage_for_optional_range_impl,
     parse_bounded_u32 as parse_bounded_u32_impl, round_to as round_to_impl,
 };
 use crate::GatewayError;
@@ -61,14 +60,6 @@ pub(crate) fn admin_stats_bad_request_response(detail: String) -> Response<Body>
     admin_stats_bad_request_response_impl(detail)
 }
 
-pub(crate) async fn list_usage_for_optional_range(
-    state: &AdminAppState<'_>,
-    time_range: Option<&AdminStatsTimeRange>,
-    filters: &AdminStatsUsageFilter,
-) -> Result<Vec<aether_data_contracts::repository::usage::StoredRequestUsageAudit>, GatewayError> {
-    list_usage_for_optional_range_impl(state, time_range, filters).await
-}
-
 pub(crate) fn parse_bounded_u32(
     field: &str,
     value: &str,