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/Plex.md

@@ -27,7 +27,7 @@ public traffic can be fronted by Caddy like every other vhost.
 | Runtime | podman quadlet, `plex.service` (user manager) — migrated from the native `plexmediaserver.service` OS-package unit (2026-09) |
 | Image | `lscr.io/linuxserver/plex:1.43.5.11029-6bf8af3f0-ls329` (pinned; verified == the registry's `latest` manifest digest at pin time: `sha256:8f655bad…e9e2334`) |
 | Data root | `/var/lib/plexmediaserver` bind-mounted **in place** as `/config` (RW) — the migration moved zero bytes |
-| Media | `/mnt/media` (the [[Media Metadata View]] overlay) bound at the same absolute path `/mnt/entropy` **read-only** — every library path in the PMS database stayed valid, zero re-scan |
+| Media | `/var/lib/media-meta/view` (the [[Media Metadata View]] overlay) bound at the same absolute path `/mnt/entropy` **read-only** — every library path in the PMS database stayed valid, zero re-scan |
 | Identity | fleet rootless model — container root maps to the `dank` user (1000:1000); the deployer chowns the data root on first cutover |
 | Port | `32400/tcp` published on `0.0.0.0` — zero client reconfiguration |
 | Network | `dankserver_appnet`, alias `plex`; Tautulli reaches it at `http://plex:32400` |