feat: add workspace account page and mobile app shell

Normalize the UI with shared primitives, add a workspace-backed account surface, and improve authenticated mobile navigation, map behavior, and dashboard browsing.

src/lib/cn.ts

@@ -0,0 +1,6 @@
+import { clsx, type ClassValue } from 'clsx';
+import { twMerge } from 'tailwind-merge';
+
+export function cn(...inputs: ClassValue[]) {
+  return twMerge(clsx(inputs));
+}