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/app.rs

@@ -6,7 +6,8 @@ use aether_runtime::{ConcurrencyGate, DistributedConcurrencyGate};
 
 use super::super::async_task::{VideoTaskPollerConfig, VideoTaskService};
 use super::super::cache::{
-    AuthApiKeyLastUsedCache, AuthContextCache, DirectPlanBypassCache, SchedulerAffinityCache,
+    AuthApiKeyLastUsedCache, AuthContextCache, DashboardResponseCache, DirectPlanBypassCache,
+    SchedulerAffinityCache,
 };
 use super::super::data::GatewayDataState;
 use super::super::fallback_metrics;
@@ -35,6 +36,7 @@ pub struct AppState {
     pub(crate) oauth_refresh: Arc<provider_transport::LocalOAuthRefreshCoordinator>,
     pub(crate) direct_plan_bypass_cache: Arc<DirectPlanBypassCache>,
     pub(crate) scheduler_affinity_cache: Arc<SchedulerAffinityCache>,
+    pub(crate) dashboard_response_cache: Arc<DashboardResponseCache>,
     pub(crate) fallback_metrics: Arc<fallback_metrics::GatewayFallbackMetrics>,
     pub(crate) frontdoor_cors: Option<Arc<FrontdoorCorsConfig>>,
     pub(crate) frontdoor_user_rpm: Arc<FrontdoorUserRpmLimiter>,