feat(dashboard): provider stats API endpoint and dashboard page (#3175)

Provider stats dashboard + API (SQL moved to db module per Hard Rule #5, +test). Integrated into release/v3.8.10.

src/shared/constants/sidebarVisibility.ts

@@ -35,6 +35,7 @@ export const HIDEABLE_SIDEBAR_ITEM_IDS = [
   "analytics-compression",
   "analytics-search",
   "analytics-evals",
+  "provider-stats",
   // Monitoring — flat
   "activity",
   "logs",
@@ -374,6 +375,13 @@ const ANALYTICS_ITEMS: readonly SidebarItemDefinition[] = [
     subtitleKey: "analyticsEvalsSubtitle",
     icon: "labs",
   },
+  {
+    id: "provider-stats",
+    href: "/dashboard/provider-stats",
+    i18nKey: "providerStats",
+    subtitleKey: "providerStatsSubtitle",
+    icon: "speed",
+  },
 ];
 
 const MONITORING_ITEMS: readonly SidebarItemDefinition[] = [