feat(usage): 改进请求追踪与缓存预热

- 区分请求重试与故障转移：新增 has_retry 标识亲和缓存重试
- 修正候选 TTFB 计算：记录候选自身的首字节时间而非全局时间
- Streaming 状态同步 rate_multiplier，支持按 API 格式配置
- 新增缓存预热服务：启动时预热仪表盘统计、热力图、每日统计
- 优化缓存 TTL 配置：仪表盘统计 2 分钟、热力图和每日统计 10 分钟
- 自动刷新间隔从 10 秒调整为 5 秒

src/api/dashboard/routes.py

@@ -11,6 +11,7 @@ from sqlalchemy.orm import Session
 from src.api.base.adapter import ApiAdapter, ApiMode
 from src.api.base.admin_adapter import AdminApiAdapter
 from src.api.base.pipeline import ApiRequestPipeline
+from src.config.constants import CacheTTL
 from src.core.enums import UserRole
 from src.database import get_db
 from src.models.database import ApiKey, Provider, RequestCandidate, StatsDaily, StatsDailyModel, Usage
@@ -177,7 +178,7 @@ class DashboardStatsAdapter(DashboardAdapter):
 
 
 class AdminDashboardStatsAdapter(AdminApiAdapter):
-    @cache_result(key_prefix="dashboard:admin:stats", ttl=60, user_specific=False)
+    @cache_result(key_prefix="dashboard:admin:stats", ttl=CacheTTL.DASHBOARD_STATS, user_specific=False)
     async def handle(self, context):  # type: ignore[override]
         """管理员仪表盘统计 - 使用预聚合数据优化性能"""
         from zoneinfo import ZoneInfo
@@ -786,7 +787,7 @@ class DashboardProviderStatusAdapter(DashboardAdapter):
 class DashboardDailyStatsAdapter(DashboardAdapter):
     days: int
 
-    @cache_result(key_prefix="dashboard:daily:stats", ttl=300, user_specific=True)
+    @cache_result(key_prefix="dashboard:daily:stats", ttl=CacheTTL.DASHBOARD_DAILY, user_specific=True)
     async def handle(self, context):  # type: ignore[override]
         from zoneinfo import ZoneInfo
         from src.services.system.stats_aggregator import APP_TIMEZONE