feat(mobile): add mobile summary view for 320-428px viewports (Sprint 4c)

Read-only capacity snapshot with utilization donut, top 5 active projects,
open demand alert banner, and quick-link grid — single-column card layout
optimised for PWA standalone mode.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web/src/app/(app)/mobile/page.tsx

@@ -0,0 +1,9 @@
+import { MobileSummaryClient } from "~/components/mobile/MobileSummaryClient.js";
+
+export const metadata = {
+  title: "CapaKraken — Mobile Summary",
+};
+
+export default function MobilePage() {
+  return <MobileSummaryClient />;
+}