perf(gateway): 为 dashboard 接口添加短时响应缓存

新增 DashboardResponseCache，对 stats/daily_stats/provider_status
三个接口按用户维度缓存 15-30 秒，减少重复数据库查询。

apps/aether-gateway/src/state/core.rs

@@ -22,8 +22,8 @@ use super::super::async_task::{
     spawn_video_task_poller, VideoTaskPollerConfig, VideoTaskService, VideoTaskTruthSourceMode,
 };
 use super::super::cache::{
-    AuthApiKeyLastUsedCache, AuthContextCache, DirectPlanBypassCache, SchedulerAffinityCache,
-    SchedulerAffinitySnapshotEntry, SchedulerAffinityTarget,
+    AuthApiKeyLastUsedCache, AuthContextCache, DashboardResponseCache, DirectPlanBypassCache,
+    SchedulerAffinityCache, SchedulerAffinitySnapshotEntry, SchedulerAffinityTarget,
 };
 use super::super::data::{GatewayDataConfig, GatewayDataState};
 use super::super::fallback_metrics;
@@ -144,6 +144,7 @@ impl AppState {
             oauth_refresh: Arc::new(provider_transport::LocalOAuthRefreshCoordinator::new()),
             direct_plan_bypass_cache: Arc::new(DirectPlanBypassCache::default()),
             scheduler_affinity_cache: Arc::new(SchedulerAffinityCache::default()),
+            dashboard_response_cache: Arc::new(DashboardResponseCache::default()),
             fallback_metrics: Arc::new(fallback_metrics::GatewayFallbackMetrics::default()),
             frontdoor_cors: None,
             frontdoor_user_rpm: Arc::new(FrontdoorUserRpmLimiter::new(