fix(dankserver): mount /mnt/entropy from its LUKS mapper at boot

The crypttab entry named the md RAID array UUID (61bd6eaf-...) where a luks
entry takes the LUKS container UUID (cd86c728-...), so
systemd-cryptsetup@entropy.service could never produce /dev/mapper/entropy and
the fstab entry could not resolve either; the volume only appeared when a
desktop session let udisks2 unlock it, which kept the broken boot path hidden
for a year. The keyfile was wrong as well: 27 bytes, i.e. the 26-character
passphrase plus a trailing newline, and cryptsetup hashes the file whole.

Records the host config as dankserver/host/{crypttab,fstab} (the dankclaw/host
precedent), rewrites the Entropy Volume page to own the chain, the UUID law and
the keyfile contract, and comments out the now-unmountable /dev/md0 line.

Proven on the host: /etc/{crypttab,fstab} byte-identical to the repo copies,
reboot into 7.0.0-42-generic mounts /mnt/entropy from /dev/mapper/entropy, all
12 containers returned, frank-archon back to 141 t/s (was 6.7 t/s on a wedged
amdgpu queue). ./tests/run.sh: ALL TESTS PASSED (749).

serverAppConfigs-docs/index.md

@@ -48,7 +48,7 @@ is a locator: one row, one clause, no numbers.
 | [[Calibre-Web]] | Calibre-Web is a web application that browses, reads, and downloads eBooks from an existing Calibre library database. |
 | [[Copyparty]] | Copyparty is a lightweight file server and media streamer that runs as a single Python binary. |
 | [[Dankserver Stack]] | Service inventory and routing overview for the media and library host. |
-| [[Entropy Volume]] | The Dankserver entropy volume is a RAID-backed LUKS filesystem mounted at |
+| [[Entropy Volume]] | Dankserver's /mnt/entropy volume: the LUKS/array chain, the crypttab + fstab boot path, and the containers bound to it |
 | [[Jellyfin]] | Jellyfin on Dankserver: quadlet unit, overlay metadata view, provider keys, ports, access, transcode status. |
 | [[mariadb]] | The MariaDB backend for RomM: quadlet unit, network alias, env-file secret handling, and the backup path. |
 | [[Media Audiobook Relayout]] | Re-filing /mnt/entropy/Audiobooks by Plex's chapter rows: narrator shelves, no renumbering, the refusals. |