feat: add shadcn/ui

frontend/package.json

@@ -12,15 +12,22 @@
     "prebuild": "node scripts/copy-monaco.mjs"
   },
   "dependencies": {
+    "@base-ui/react": "^1.7.0",
+    "@fontsource-variable/inter": "^5.3.0",
     "@monaco-editor/react": "^4.7.0",
     "@react-router/node": "^8",
     "@react-router/serve": "^8",
+    "class-variance-authority": "^0.7.1",
+    "clsx": "^2.1.1",
     "isbot": "^5.1.36",
     "lucide-react": "^1.33.0",
     "monaco-editor": "^0.56.0",
     "react": "^19.2.7",
     "react-dom": "^19.2.7",
     "react-router": "^8",
+    "shadcn": "^4.19.0",
+    "tailwind-merge": "^3.6.0",
+    "tw-animate-css": "^1.4.0",
     "zustand": "^5.0.14"
   },
   "devDependencies": {