Migrate apps/web to shadcn/ui with preset b2D1F1IZv

Replace custom CSS module UI with shadcn radix-luma components,
Tailwind v4, and Manrope font. Remove packages/ui.

apps/web/lib/utils.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));
+}