refactor(media): mount the view inside /var/lib/media-meta instead of under /mnt

The merged door was /mnt/media, which read like a third volume and split the host
state across two trees. It is now /var/lib/media-meta/view, so the array layer,
the SSD upper layer, the kernel workdir, the reap trash and the merged tree are
one directory — and the mount table gains no new /mnt entry beside the array.

systemd names a mount unit after its ESCAPED path, so the repo copy keeps the
readable name media-meta-view.mount while `install` writes the host file as
var-lib-media\x2dmeta-view.mount; `plan` prints both and the page records them, so
nobody hunts for a unit that "does not exist". install also creates the mount
point itself, because systemd will not.

The seam now additionally pins that the unit's Where= is exactly the path both
containers bind — guard and bind cannot drift apart. The Quadlet Lifecycle
phantom-path example is corrected too: it named an invented /mnt/media/*, while
the real phantom is the legacy /opt/jellyfin/* that dankserver/compose.yaml still
carries for a service whose roots moved to /home/dank/Containers/jellyfin.

serverAppConfigs-docs/Dankserver/Media Relayout.md

@@ -257,7 +257,7 @@ show. A name whose marker is `Part 2` is a film and stays put.
   the same command with `--apply`: the sidecars left at the old coordinates become
   ghost folders — artwork and an `.nfo` with no video — that both servers browse
   and report as content.
-- **Nothing deletes through `/mnt/media`.** A delete there writes an overlayfs
+- **Nothing deletes through the metadata view.** A delete there writes an overlayfs
   whiteout in the upper layer, which hides the array's copy without removing it;
   the file returns when the view is unmounted. Deletions in this pipeline happen
   on the raw path only, which is what the journal can undo.