feat: setup Tailwind CSS and initial routing structure

Configure @tailwindcss/vite in Nuxt config
Add default layout and main CSS file
Create initial index and login pages
Replace default Nuxt welcome screen with page routing

package.json

@@ -14,5 +14,9 @@
     "nuxt": "^4.4.2",
     "vue": "^3.5.32",
     "vue-router": "^5.0.4"
+  },
+  "devDependencies": {
+    "@tailwindcss/vite": "^4.2.2",
+    "tailwindcss": "^4.2.2"
   }
 }