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/index.css

@@ -1,3 +1,6 @@
+@import "@fontsource-variable/schibsted-grotesk";
+@import "./styles/tokens.css";
+
 @tailwind base;
 @tailwind components;
 @tailwind utilities;
@@ -14,7 +17,8 @@ body,
 
 body {
   margin: 0;
-  font-family: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
+  font-family: var(--sp-font);
+  background: var(--sp-bg);
 }
 
 /* Custom scrollbar */