wiki: add firewalld mail ports reset article + session updates

- New article: firewalld mail ports wiped after reload (IMAP + webmail outage)
- New article: Plex 4K codec compatibility (Apple TV)
- New article: mdadm RAID recovery after USB hub disconnect
- Updated yt-dlp article
- Updated all index files: SUMMARY.md, index.md, README.md, category indexes
- Article count: 41 → 42

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

SUMMARY.md

@@ -30,9 +30,11 @@
     * [yt-dlp: Video Downloading](03-opensource/media-creative/yt-dlp.md)
 * [Streaming & Podcasting](04-streaming/index.md)
     * [OBS Studio Setup & Encoding](04-streaming/obs/obs-studio-setup-encoding.md)
+    * [Plex 4K Codec Compatibility (Apple TV)](04-streaming/plex/plex-4k-codec-compatibility.md)
 * [Troubleshooting](05-troubleshooting/index.md)
     * [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)
     * [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)
@@ -42,3 +44,4 @@
     * [MajorWiki Setup & Publishing Pipeline](05-troubleshooting/majwiki-setup-and-pipeline.md)
     * [Gitea Actions Runner: Boot Race Condition Fix](05-troubleshooting/gitea-runner-boot-race-network-target.md)
     * [SELinux: Fixing Dovecot Mail Spool Context (/var/vmail)](05-troubleshooting/selinux-dovecot-vmail-context.md)
+    * [mdadm RAID Recovery After USB Hub Disconnect](05-troubleshooting/storage/mdadm-usb-hub-disconnect-recovery.md)