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.

scripts/deploy-remote.sh

@@ -1204,9 +1204,10 @@ deploy_romm_stack() {
 
 ensure_media_view() {
     # Both media servers read their library through the SSD-backed overlay view
-    # (scripts/media-view.sh, dankserver/host/systemd/mnt-media.mount): the array
-    # below stays read-only and every sidecar Jellyfin writes lands on the NVMe.
-    # Raise it BEFORE either container starts — a start against a bare /mnt/media
+    # (scripts/media-view.sh, dankserver/host/systemd/media-meta-view.mount): the
+    # array below stays read-only and every sidecar Jellyfin writes lands on the
+    # NVMe.
+    # Raise it BEFORE either container starts — a start against a bare view
     # directory would let a scan clear the library database. The units also carry
     # ConditionPathIsMountPoint, so a missing view skips the start rather than
     # damaging anything. A relayout must be followed by `media-view.sh reap`