feat(backend): add /healthz endpoint (#13834)

* feat(backend): add /healthz endpoint

* feat(backend): also check meilisearch status if available

* style: header

* chore: no-store

* chore: healthcheck.sh

* style: format

healthcheck.sh

@@ -4,4 +4,4 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 PORT=$(grep '^port:' /misskey/.config/default.yml | awk 'NR==1{print $2; exit}')
-curl -s -S -o /dev/null "http://localhost:${PORT}"
+curl -Sfso/dev/null "http://localhost:${PORT}/healthz"