feat(booth): add The Booth — ephemeral media drop board for CC sessions

A standing user-level web server (nh3-dev :8090) that renders drop-folders
under ~/booth-data as ephemeral media "booths" so Claude Code sessions can
surface A/B renders and smoke results to the operator, then let them self-wipe.

- Scan-and-serve model, no database, no upload API — a booth is just a folder.
  A folder's own index.html is served verbatim; otherwise an auto-gallery of
  images / webm+mp4 video / audio is rendered, with <file>.txt caption sidecars
  folded in (labels A/B pairs).
- 24h TTL from newest mtime in the tree; background sweeper wipes stale booths.
- Path-traversal + symlink-escape guarded; delete via UI button or DELETE API.
- FastAPI + Jinja2, runs from the checkout under systemctl --user (booth.service),
  alongside the other nh3-dev fleet sidecars. 15 tests, all green.
- Homepage tile added (Apps -> The Booth, siteMonitor /healthz).
- Harden the homepage rsync doc: exclude *.bak* and logs/ so --delete can't
  wipe the host's dated services.yaml backups (footgun found deploying this).

configs/homepage/README.md

@@ -85,12 +85,21 @@ Current workflow — push this directory onto the host:
 ```bash
 rsync -av --delete \
   --exclude='.env' --exclude='.env.*' \
+  --exclude='*.bak*' --exclude='logs/' \
   configs/homepage/ esh-docker-vm:/opt/docker/conf/homepage/
 ```
 
 The real `.env` lives on `esh-docker-vm` next to the compose file and must
 not be overwritten (holds Plex/Jellyfin keys).
 
+> **`--delete` footgun (learned 2026-07-20):** the host keeps dated
+> `services.yaml.bak-*` safety copies and a live `logs/` dir that are *not*
+> in this repo. A bare `--delete` rsync wipes both. The `--exclude='*.bak*'`
+> and `--exclude='logs/'` above protect them. For a one-file tweak, skip
+> `--delete` entirely and push the single file:
+> `rsync -av configs/homepage/services.yaml esh-docker-vm:/opt/docker/conf/homepage/services.yaml`
+> (back up the host copy first: `ssh esh-docker-vm 'cp -a …/services.yaml …/services.yaml.bak-<date>-<what>'`).
+
 The homepage container reloads most files on-change; if a new group in
 `settings.yaml` doesn't show up, `docker compose restart` on the host.