GHSA-hg3f-28rg-4jxj: Nuxt's route middleware is not enforced when rendering `.server.vue` pages via `/__nuxt_island/page_*`

Summary When experimental.componentIslands is enabled (default in Nuxt 4), any .server.vue file under pages/ is automatically registered as a server island under the key page_<routeName> and exposed via the /__nuxt_island/:name endpoint. Until this fix, requests through that endpoint rendered the page component directly via the SSR renderer without instantiating Vue Router, which meant route middleware declared on the page (including definePageMeta({ middleware })) did not run. For Nuxt applications that gate a .server.vue *page* behind route middleware as their sole auth check, an unauthenticated attacker could bypass that check by requesting /__nuxt_island/page_<routeName>_<anyhash> directly and receiving the server-rendered HTML. Affected configurations All three conditions must hold for an application to be vulnerable: 1. experimental.componentIslands is enabled (the default in Nuxt 4; opt-in in Nuxt 3). 2. The application defines one or more .server.vue files under pages/, registering them as routed pages. 3. Authentication / authorization for at least one such page is enforced solely via route middleware (middleware/*.ts referenced from definePageMeta), without a server-side check inside the page or its data layer. Applications that enforce auth inside the island's own data layer (server-only API routes, useRequestEvent + manual session checks, etc.) were not affected. The general "route middleware does not run for non-page island *components*" behaviour is documented and unchanged; this advisory concerns the .server.vue *page* case specifically, where running middleware is the user's clear expectation. Details - Build (packages/nuxt/src/components/templates.ts): .server.vue pages are registered as island components with page_ prefix, making them addressable through /__nuxt_island/page_<routeName>_<hashId>. - Runtime (packages/nitro-server/src/runtime/handlers/island.ts): the handler resolves the requested island component and renders it via renderer.r