Migrate to the cn package

- Ran `npx shadcn@latest migrate cn`: swaps clsx + tailwind-merge for cn
- Import cn from "cn" everywhere (matches what `shadcn add` now writes)
  and remove the src/lib/utils.js re-export shim

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/app/components/ContactButtons.js

@@ -1,7 +1,7 @@
 import Link from "next/link";
 import { MessageCircle, MessageSquare, Phone } from "lucide-react";
 import { Button } from "@/components/ui/button";
-import { cn } from "@/lib/utils";
+import { cn } from "cn";
 import { business, links } from "@/lib/site";
 
 // Call / Text (and optionally WhatsApp and Get a quote) buttons.