fix(nextcloud): add internal hostname to trusted_domains

Add 'nextcloud' to NEXTCLOUD_TRUSTED_DOMAINS so internal callbacks
from other containers (e.g. OnlyOffice Document Server) arriving with
Host: nextcloud are not rejected. Only affects initial install — for
existing deployments, the integration handler sets it via occ.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

templates/nextcloud/docker-compose.yml

@@ -29,7 +29,7 @@ services:
       - MYSQL_HOST=nextcloud-db
       - NEXTCLOUD_ADMIN_USER=${NEXTCLOUD_ADMIN_USER:-admin}
       - NEXTCLOUD_ADMIN_PASSWORD=${NEXTCLOUD_ADMIN_PASSWORD}
-      - NEXTCLOUD_TRUSTED_DOMAINS=${SUBDOMAIN}.${DOMAIN}
+      - NEXTCLOUD_TRUSTED_DOMAINS=${SUBDOMAIN}.${DOMAIN} nextcloud
       - OVERWRITEPROTOCOL=https
       - OVERWRITEHOST=${SUBDOMAIN}.${DOMAIN}
       - REDIS_HOST=nextcloud-redis