feat: add Models dashboard tab with rich per-model analytics

- New /models page in left nav (after Analytics)
- New /api/analytics/models endpoint with per-model token/cost/session
  breakdown, cache read/reasoning tokens, tool calls, avg tokens/session,
  and capabilities from models.dev (vision/tools/reasoning/context window)
- Model cards with stacked token distribution bar, capability badges,
  provider badges, cost info, and relative time
- Summary stats bar (models used, total tokens, est. cost, sessions)
- Period selector (7d/30d/90d) with refresh
- i18n support (en + zh)

web/src/App.tsx

@@ -20,6 +20,7 @@ import {
   BookOpen,
   Clock,
   Code,
+  Cpu,
   Database,
   Download,
   Eye,
@@ -61,6 +62,7 @@ import EnvPage from "@/pages/EnvPage";
 import SessionsPage from "@/pages/SessionsPage";
 import LogsPage from "@/pages/LogsPage";
 import AnalyticsPage from "@/pages/AnalyticsPage";
+import ModelsPage from "@/pages/ModelsPage";
 import CronPage from "@/pages/CronPage";
 import SkillsPage from "@/pages/SkillsPage";
 import ChatPage from "@/pages/ChatPage";
@@ -96,6 +98,7 @@ const BUILTIN_ROUTES_CORE: Record<string, ComponentType> = {
   "/": RootRedirect,
   "/sessions": SessionsPage,
   "/analytics": AnalyticsPage,
+  "/models": ModelsPage,
   "/logs": LogsPage,
   "/cron": CronPage,
   "/skills": SkillsPage,
@@ -125,6 +128,12 @@ const BUILTIN_NAV_REST: NavItem[] = [
     label: "Analytics",
     icon: BarChart3,
   },
+  {
+    path: "/models",
+    labelKey: "models",
+    label: "Models",
+    icon: Cpu,
+  },
   { path: "/logs", labelKey: "logs", label: "Logs", icon: FileText },
   { path: "/cron", labelKey: "cron", label: "Cron", icon: Clock },
   { path: "/skills", labelKey: "skills", label: "Skills", icon: Package },
@@ -142,6 +151,7 @@ const ICON_MAP: Record<string, ComponentType<{ className?: string }>> = {
   Activity,
   BarChart3,
   Clock,
+  Cpu,
   FileText,
   KeyRound,
   MessageSquare,