Phase 24: Design System v2 — analytics-style UI (0.30.0)

- New /api/dashboard/funnel (5-stage stack health, 30s TTL cache) and
  /api/dashboard/summary (containers, daily uptime jsonl, ops activity)
- Token system (tokens.css + Tailwind sp-* aliases); legacy bg/card/accent
  remapped onto the tokens; Schibsted Grotesk bundled via fontsource
- TopNav pill navigation + AppShell replace the sidebar layout (off-canvas
  drawer below 1024px); central display-weight page titles
- Dashboard redesign: FunnelChart (gradient/hatch SVG waterfall), container
  count card with per-host bars + Insights chip, UptimeChart, OpsGrid,
  AiPromptBar; 30/7-day range selector; host sections retained below
- Stacks page honours ?q= / ?filter= deep links + new status-filter select

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/App.tsx

@@ -1,6 +1,6 @@
 import { useEffect } from "react";
 import { BrowserRouter, Navigate, Outlet, Route, Routes } from "react-router-dom";
-import { Layout } from "@/components/layout/Layout";
+import { AppShell } from "@/components/layout/AppShell";
 import { Login } from "@/pages/Login";
 import { Dashboard } from "@/pages/Dashboard";
 import { Stacks } from "@/pages/Stacks";
@@ -40,7 +40,7 @@ export default function App() {
       <Routes>
         <Route path="/login" element={<Login />} />
         <Route element={<RequireAuth />}>
-          <Route element={<Layout />}>
+          <Route element={<AppShell />}>
             <Route path="/" element={<Dashboard />} />
             <Route path="/stacks" element={<Stacks />} />
             <Route path="/stacks/new" element={<StackEditor />} />