Decommission LXC 109 (syncthing)

Container had been stopped since 2026-04-21 and was never re-enabled.
pct destroy 109 --purge cleaned up vm-109-disk-0 on local-lvm and the
config file. /mnt/library/syncthing subtree was already empty at the
time of destruction and is retained as an empty dir (no real data to
migrate or back up).

- README.md, containers/index.md: removed row, moved to "recently
  destroyed" table
- hosts/hubris.md: dropped from /mnt/library subtree list, updated
  containers/index summary line, added changelog entry
- infrastructure/media-permissions.md: dropped from membership table
  and onboarding example, generalised pct-exec gotcha hostname,
  added changelog
- vms/100-zimaos.md: dropped from "existing fleet" enumeration
- containers/102-nfs-export.md: dropped from bind-mount sibling list
  (7 LXCs now, not 8)
- containers/109-syncthing.md: deleted

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

containers/102-nfs-export.md

@@ -8,14 +8,14 @@ Dedicated, single-purpose LXC that re-exports `/mnt/library` over NFSv4 to clien
 - **LAN DNS:** `nfs-export.hubris.network` → `192.168.8.200` (direct, no Caddy)
 - **Privilege:** privileged (`unprivileged: 0`) + `lxc.apparmor.profile: unconfined` — required for `nfs-kernel-server`
 - **Resources:** 1 core / 512 MiB RAM / 2 GiB rootfs / 256 MiB swap
-- **Mounts:** host `/mnt/library` ↔ container `/mnt/library` (same path on both sides — matches the bind-mount convention used by jellyfin, paperless, arriman, nextcloud, mule-images, plato, syncthing, apps)
+- **Mounts:** host `/mnt/library` ↔ container `/mnt/library` (same path on both sides — matches the bind-mount convention used by jellyfin, paperless, arriman, nextcloud, mule-images, plato, apps)
 
 ## What it does
 
 ```
 /mnt/library (host ext4 on nvme1n1)
         │
-        ├── bind-mounted into 8 other LXCs (jellyfin, paperless, …)
+        ├── bind-mounted into 7 other LXCs (jellyfin, paperless, …)
         └── bind-mounted into LXC 102
                     │
                     └── nfs-kernel-server exports /mnt/library