wiki: document Nextcloud AIO 20h unhealthy incident and watchdog cron fix

Add troubleshooting article for the 2026-03-27 incident where PHP-FPM
hung after the nightly update cycle. Update the Netdata Docker alarm
tuning article with the dedicated Nextcloud alarm split and the new
watchdog cron deployed to majorlab. (54 articles)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

SUMMARY.md

@@ -44,6 +44,7 @@
     * [Mail Client Stops Receiving: Fail2ban IMAP Self-Ban](05-troubleshooting/networking/fail2ban-imap-self-ban-mail-client.md)
     * [firewalld: Mail Ports Wiped After Reload](05-troubleshooting/networking/firewalld-mail-ports-reset.md)
     * [Tailscale SSH: Unexpected Re-Authentication Prompt](05-troubleshooting/networking/tailscale-ssh-reauth-prompt.md)
+    * [Nextcloud AIO Unhealthy 20h After Nightly Update](05-troubleshooting/docker/nextcloud-aio-unhealthy-20h-stuck.md)
     * [Docker & Caddy Recovery After Reboot (Fedora + SELinux)](05-troubleshooting/docker-caddy-selinux-post-reboot-recovery.md)
     * [ISP SNI Filtering with Caddy](05-troubleshooting/isp-sni-filtering-caddy.md)
     * [Obsidian Vault Recovery — Loading Cache Hang](05-troubleshooting/obsidian-cache-hang-recovery.md)