wiki: add Tailscale SSH reauth article; update Netdata Docker alarm tuning (50 articles)

- New: Tailscale SSH unexpected re-authentication prompt — diagnosis and fix
- Updated: netdata-docker-health-alarm-tuning — add delay: up 3m to suppress
  Nextcloud AIO PHP-FPM ~90s startup false alerts; update settings table and notes
- Updated: 05-troubleshooting/index.md and SUMMARY.md

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

SUMMARY.md

@@ -40,6 +40,7 @@
     * [Apache Outage: Fail2ban Self-Ban + Missing iptables Rules](05-troubleshooting/networking/fail2ban-self-ban-apache-outage.md)
     * [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)
     * [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)