docs: fix nas_media docker volume opts after 2026-09-16 outage

Host reboot broke the nas_media Docker NFS volume for 6+ hours (plex,
qbittorrent x3, navidrome, sonarr, jellyfin all down): nfs-utils 2.6.4 no
longer accepts the ":/path" + addr= device split, and separately Docker's
local volume driver can't do nfsvers=4 (calls mount(2) directly, skipping
the mount.nfs helper's version negotiation). Volume recreated with an
explicit host:/path device and vers=3. Updating docs/comments to match
the corrected live config so the next person doesn't recreate the same
broken volume from the stale example.

torrents/docker-compose.yaml

@@ -53,13 +53,17 @@ services:
       - nas_media:/data
 
 volumes:
+  # External volume; actual definition lives in `docker volume create` (see
+  # NAS-CONNECTION-STRATEGIES.md). Current opts (fixed 2026-09-16 after a
+  # host reboot broke this): type=nfs, vers=3 (not 4 - Docker's local volume
+  # driver calls mount(2) directly rather than through the mount.nfs
+  # userspace helper, which fails with "protocol not supported" for
+  # nfsvers=4 on current nfs-utils/kernel), device=192.168.1.192:/mnt/user/media
+  # (host must be in the device string itself now, not split into a
+  # separate addr= option - nfs-utils 2.6.4 on Ubuntu 24.04 no longer
+  # accepts the old ":/path" + addr= form).
   nas_media:
     external: true
-#    driver: local
-#    driver_opts:
-#      type: nfs
-#      o: "addr=192.168.1.192,rw,nolock,soft"
-#      device: ":/mnt/user/media"
 
 networks:
   default: