Refactor: Migrar UI completa a Tailwind CSS v4 + shadcn-vue

- Reemplazar CSS nativo con Tailwind CSS v4 y utilidades custom
- Crear librería de componentes UI basada en shadcn-vue (Radix Vue)
- Componentes UI: Button, Card, Input, Textarea, Badge, Dialog, Avatar, DropdownMenu
- Migrar todos los componentes existentes a Tailwind utilities
- Convertir EventCard.js (htm) a EventCard.vue (SFC)
- Implementar sistema de temas dark/light con clase .dark
- Mantener efectos glassmorphism via @utility custom
- Eliminar styles.css legacy

frontend/package.json

@@ -9,11 +9,17 @@
     "preview": "vite preview"
   },
   "dependencies": {
-    "vue": "^3.4.38",
-    "htm": "^3.1.1"
+    "class-variance-authority": "^0.7.1",
+    "clsx": "^2.1.1",
+    "htm": "^3.1.1",
+    "radix-vue": "^1.9.17",
+    "tailwind-merge": "^3.4.0",
+    "vue": "^3.4.38"
   },
   "devDependencies": {
+    "@tailwindcss/vite": "^4.1.17",
     "@vitejs/plugin-vue": "^5.0.5",
+    "tailwindcss": "^4.1.17",
     "vite": "^5.4.8"
   }
 }