Migrate from nuxt-maintenizr

Move from build-time routing to live state.

Replace nuxt-maintenizr with nuxt-maintainer; rename config key maintenizr to maintainer.
Remove .nuxtrc flags and /maintenance overrides. State now lives in the configured Unstorage mount.
Compose <NuxtMaintenanceError> into the existing error.vue.
Replace old CLI commands with npx nuxt-maintainer ....
Remove compatibility assumptions: version 1 intentionally ships no old aliases.

The new commands affect a running SSR server immediately. Test the error page and bypass in staging before switching automation.

Named sections

Present maintenance fallbacks for part of a page.