perf(usage): heatmap 改为数据库端按天聚合查询

将 admin 和 user heatmap 从逐条加载 usage audit 记录后在应用层聚合,
改为通过 SQL GROUP BY DATE 在数据库端直接按天汇总, 大幅减少数据传输量。

新增 UsageDailyHeatmapQuery / StoredUsageDailySummary 类型,
在 trait、SQL、内存实现中均补齐 summarize_usage_daily_heatmap 方法。

同时优化 docker-compose: postgres 增加空闲事务超时与 keepalive 参数,
gateway 增加健康检查配置。

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

@@ -3,6 +3,6 @@ mod types;
 pub use types::{
     parse_usage_body_ref, usage_body_ref, StoredProviderApiKeyUsageSummary,
     StoredProviderUsageSummary, StoredProviderUsageWindow, StoredRequestUsageAudit,
-    UpsertUsageRecord, UsageAuditListQuery, UsageBodyField, UsageReadRepository, UsageRepository,
-    UsageWriteRepository,
+    StoredUsageDailySummary, UpsertUsageRecord, UsageAuditListQuery, UsageBodyField,
+    UsageDailyHeatmapQuery, UsageReadRepository, UsageRepository, UsageWriteRepository,
 };