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-plan.py

@@ -422,7 +422,7 @@ def services_for_path(path: str, target: str) -> set[str]:
             }
             _add(services, *quadlet_services.get(parts[1], set()))
         if len(parts) >= 2 and parts[1] == "host":
-            # dankserver/host/systemd/mnt-media.mount is the overlay view the two
+            # dankserver/host/systemd/media-meta-view.mount is the overlay view the
             # media servers bind (scripts/media-view.sh installs it on the host),
             # so editing it restarts jellyfin and plex and nothing else.
             _add(services, "jellyfin", "plex")