stacks(park): mirror stonehenge-park v1.0.0-beta.1 deploy on nh3-docker

New self-contained stack (FastAPI + SQLite + in-process scheduler) from
vh/stonehenge-park tag v1.0.0-beta.1, deployed to nh3-docker per park-dev's
operator-approved request. Port 8420, LAN/WG-internal; park-data volume (SQLite
sole source of truth) covered by the host's /var/lib/docker/volumes restic source.
Image built locally (no registry yet); .env carries PARK_API_KEY from the vault.
althing push to henge-crow deferred (PARK_ALTHING_CHANNEL empty) until althing-cli
is wired into the container.

stacks/park/compose.yaml

@@ -0,0 +1,17 @@
+# stonehenge-park — nh3-docker. LAN/WG-internal only (port 8420); NOT internet-exposed.
+# Image built once from vh/stonehenge-park v1.0.0-beta.1 (infra-ops: docker build -t park:v1.0.0-beta.1 .).
+# Build source mirror: ~/deploy-src/stonehenge-park on nh3-docker. .env (chmod 600) holds PARK_API_KEY (vault nh3-dev/park-api-key).
+services:
+  park:
+    image: park:v1.0.0-beta.1
+    container_name: park
+    restart: unless-stopped
+    ports:
+      - "8420:8420"
+    env_file:
+      - .env
+    volumes:
+      - park-data:/data      # SQLite single file /data/park.db — covered by restic (via /var/lib/docker/volumes)
+
+volumes:
+  park-data: