Move auth routes to server/api/auth/

BREAKING CHANGE: Auth routes moved from /auth/* to /api/auth/*

- Move server/routes/auth/ to server/api/auth/
- Update login.vue to use /api/auth/authentik
- Update UserMenu.vue to use /api/auth/logout
- Remove old server/routes/ structure
- server/api/ is better supported in Nuxt 4

IMPORTANT: Update these in Gitea:
- Variable NUXT_OAUTH_AUTHENTIK_REDIRECT_URL to: https://seguidordelotes.nucleoriofrio.com/api/auth/authentik
- Update Authentik redirect URI to: https://seguidordelotes.nucleoriofrio.com/api/auth/authentik

nuxt4-app/server/api/auth/logout.get.ts

@@ -0,0 +1,10 @@
+/**
+ * Logout Handler
+ * Ruta: /api/auth/logout
+ *
+ * Limpia la sesión del usuario y redirige a la página de inicio
+ */
+export default defineEventHandler(async (event) => {
+  await clearUserSession(event)
+  return sendRedirect(event, '/')
+})