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

stacks/filezilla/compose.yaml

@@ -0,0 +1,24 @@
+services:
+  filezilla:
+    image: jlesage/filezilla
+    restart: unless-stopped
+    environment:
+      - PUID=2000
+      - PGID=2000
+    volumes:
+      - /home/user:/storage:rw
+      - /docker/appdata/filezilla:/config:rw
+      - /mnt/share:/NAS/share
+      - /mnt/music:/NAS/music
+      - /mnt/books:/NAS/books
+      - /mnt/media:/NAS/media
+    ports:
+      - 5800:5800
+    container_name: filezilla
+    labels:
+      - homepage.group=Apps
+      - homepage.name=FileZilla
+      - homepage.icon=si-filezilla
+      - homepage.description=Web-based FileZilla (vm-esh-nas NFS mounts)
+      - homepage.href=http://10.0.50.154:5800
+networks: {}