T1/Phase 1: scaffold Vite SPA + Hono API + Bun worker

- apps/web: Vite + React 19 + TanStack Router/Query + shadcn/ui
   - apps/api: Hono + Bun on :3001 with /api/health, /api/auth/*, /mcp stubs
   - apps/worker: Bun worker stub, DB connection, graceful SIGTERM
   - apps/web-legacy/: old Next.js code moved aside (preserved for T2-T8 reference)
   - Dockerfiles: api (Bun), worker (Bun), spa (multi-stage Caddy)
   - Caddyfile: serves dist + reverse-proxies /api/* + /mcp to api
   - docker-compose.yml: 4-service target (api, spa, db, worker)
   - packages/db/src/client.ts: shared Drizzle client for api + worker
   - db/client.ts: root-level alias for convenience

   Parent: t_e1cbd87d -> t_24c9c3fd (T0)

apps/web-legacy/app/(dashboard)/layout.tsx

@@ -0,0 +1,40 @@
+import { Sidebar } from '@/components/sidebar';
+import { TopBar } from '@/components/topbar';
+import { NetworkErrorBanner } from '@/components/network-error-banner';
+import { KeyboardShortcutsProvider } from '@/components/keyboard-shortcuts-provider';
+import { WebVitalsTracker } from '@/components/web-vitals-tracker';
+import { MobileBottomNav } from '@/components/mobile-bottom-nav';
+import { DispatchPanel } from '@/components/agents/dispatch-panel';
+import { OnboardingFlow } from '@/components/onboarding/onboarding-flow';
+
+export default function DashboardLayout({ children }: { children: React.ReactNode }) {
+  return (
+    <KeyboardShortcutsProvider>
+      <WebVitalsTracker />
+      <a href="#main-content" className="skip-link">
+        Skip to main content
+      </a>
+      <div className="flex min-h-screen">
+        <NetworkErrorBanner />
+        <Sidebar />
+        <div className="flex flex-1 flex-col pb-16 md:pb-0">
+          <TopBar />
+          <main id="main-content" className="flex-1 overflow-auto p-4 md:p-6" tabIndex={-1}>
+            {children}
+          </main>
+        </div>
+      </div>
+      <MobileBottomNav />
+      {/* Floating AI dispatch button */}
+      <div className="fixed bottom-6 right-6 z-50">
+        <DispatchPanel
+          triggerLabel="Ask AI"
+          triggerVariant="default"
+          triggerClassName="h-12 w-12 rounded-full shadow-lg md:h-auto md:w-auto md:rounded-md md:px-4 md:py-2"
+        />
+      </div>
+      <OnboardingFlow />
+      <div className="sr-only" aria-live="polite" aria-atomic="true" id="a11y-announcer" />
+    </KeyboardShortcutsProvider>
+  );
+}