fix: add pull_policy: build so Portainer builds the image locally

Portainer's git-stack deploy runs `docker compose pull` before `up`,
which tried to fetch kammergut:0.1.0 from a registry and got
"pull access denied". The image only exists locally — `pull_policy:
build` tells Compose to build from the Dockerfile instead.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -4,6 +4,10 @@ services:
       context: .
       dockerfile: Dockerfile
     image: kammergut:0.1.0
+    # Build the image locally instead of pulling from a registry —
+    # otherwise Portainer's `compose pull` step fails since this image
+    # isn't published anywhere.
+    pull_policy: build
     container_name: kammergut
     restart: unless-stopped
     ports: