fix(frontend): add missing tailwind-variants dependency

- badge.svelte imports tailwind-variants but it wasn't in package.json
- Passed locally due to persistent node_modules
- Failed in CI with fresh install
- Fixes typecheck error in CI workflow

Author: nirukk52

frontend/package.json

@@ -26,6 +26,7 @@
     "envalid": "^8.1.1",
     "lucide-svelte": "^0.425.0",
     "tailwind-merge": "^3.3.1",
+    "tailwind-variants": "^3.1.1",
     "tw-animate-css": "^1.4.0"
   },
   "devDependencies": {