Correct Ana-side NAS identity: Debian 12, not TrueNAS

Network probes (no web admin, Debian SSH banner, only file-server ports
open) show 10.250.50.50 is vanilla Debian 12 with hand-configured NFS/SMB,
reprovisioned from the original TrueNAS SCALE install. Update stack
comments, README storage notes, Backrest description, proxmox-vms.md
entry for VM 100, and the restic configs intro to match.

Cross-site sync plan simplifies to plain rsync over SSH on both sides —
no appliance-specific tooling needed.

stacks/rest-server-ana/compose.yaml

@@ -1,8 +1,9 @@
 # rest-server (Anaheim) — restic backup target for the fleet.
 #
-# Deploys to ana-docker. Data dir is on the TrueNAS NFS mount
-# (/mnt/backup/restic/repo/ana) so snapshots on the NAS side protect the
-# backup blobs themselves.
+# Deploys to ana-docker. Data dir is the NFS mount at
+# /mnt/backup/restic/repo/ana, backed by the Debian 12 NFS/SMB file
+# server at 10.250.50.50. (Historically a TrueNAS SCALE appliance; since
+# reprovisioned as vanilla Debian.)
 #
 # Mirrors stacks/rest-server-nh3/ in every meaningful way — same auth
 # model, same on-disk layout, same operational semantics — so each client
@@ -50,7 +51,7 @@ services:
       - homepage.group=PFI-ANA
       - homepage.name=Restic (rest-server)
       - homepage.icon=mdi-cloud-upload
-      - homepage.description=Anaheim restic endpoint (data on TrueNAS NFS)
+      - homepage.description=Anaheim restic endpoint (data on NFS)
       - homepage.href=http://10.250.50.70:${REST_PORT}
 
 networks: