feat(web): scaffold Next.js 16 dashboard with design system and auth client (#82)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/web/src/components/layout/app-shell.tsx

@@ -0,0 +1,19 @@
+import type { ReactNode } from 'react';
+import { Sidebar } from './sidebar';
+import { Topbar } from './topbar';
+
+interface AppShellProps {
+  children: ReactNode;
+}
+
+export function AppShell({ children }: AppShellProps): React.ReactElement {
+  return (
+    <div className="min-h-screen">
+      <Sidebar />
+      <div className="pl-sidebar">
+        <Topbar />
+        <main className="p-6">{children}</main>
+      </div>
+    </div>
+  );
+}