feat: implement auth middleware, user sync, and token state persistence

- Define useAuth composable logic with syncUser, handleLoginSuccess, and logout methods
- Add auth.ts and guest.ts route middlewares to guard routes based on authentication and user roles
- Add auth.client.ts plugin to boot-sync logged in user details
- Declare custom PageMeta type definitions to support role-based authorization rules

app/middleware/guest.ts

@@ -0,0 +1,17 @@
+export default defineNuxtRouteMiddleware(async () => {
+  const auth = useAuth()
+
+  // Se c'è un token ma l'utente non è ancora caricato e non stiamo già sincronizzando, sincronizza
+  if ((auth.token.value || auth.tokenState.value) && !auth.user.value && !auth.isSyncingUser.value) {
+    try {
+      await auth.syncUser()
+    } catch (error) {
+      console.error('[Guest Middleware] Sync failed:', error)
+    }
+  }
+
+  // Se autenticato, redirige al dashboard
+  if (auth.isAuthenticated.value && auth.user.value) {
+    return navigateTo('/dashboard')
+  }
+})