fix(filezilla): set restart: unless-stopped and canonicalize the stack

The filezilla container on vm-esh-nas shipped with no restart policy. It
was SIGTERMed during the 2026-08-18 host shutdown and never came back,
staying down four days while dockge/dozzle-agent/beszel-agent all
recovered on their own.

- add `restart: unless-stopped` (applied on the host, container recreated
  and verified serving 200 on :5800 with all four /NAS mounts visible)
- promote the previously un-canonicalized compose into stacks/filezilla/
  so the policy is version-controlled rather than host-only
- record the missing-restart-policy failure mode in the host README

servers/vm-esh-nas/README.md

@@ -42,7 +42,8 @@ scripts/refresh-server-info.sh vm-esh-nas
 ## Stack mirror layout
 
 - `stacks-mirror/vm-esh-nas/beszel-agent-esh-nas/` — Beszel agent (canonical in `stacks/beszel/`)
-- Other stacks (`dockge`, `dozzle-agent`, `filezilla`) not yet canonicalized; run `sync-stacks.sh vm-esh-nas` to pull them into the mirror.
+- `filezilla` — canonical in `stacks/filezilla/`
+- Other stacks (`dockge`, `dozzle-agent`) not yet canonicalized; run `sync-stacks.sh vm-esh-nas` to pull them into the mirror.
 
 ## Placement rule
 
@@ -52,6 +53,11 @@ VM. Low RAM ceiling (3.8 GB) — keep heavy workloads elsewhere.
 
 ## Known nits
 
+- **Check restart policies after any reboot of this host.** `dockge`,
+  `dozzle-agent`, and `beszel-agent` carry restart policies; `filezilla` did
+  not, and stayed down silently for four days after the 2026-08-18 reboot
+  (fixed 2026-08-22 — `restart: unless-stopped`). Anything else added here
+  needs the policy set explicitly.
 - `/opt/docker/compose` is world-writable (drwxrwxrwx). Harmless but
   worth tightening at some point.
 - `/opt/docker/conf` doesn't exist yet; stacks that need bind-mounted