dev-deploy: fix backend startup in CI

Two bugs surfaced on the first real merge into development:

1. `${{ env.HOME }}` evaluates to empty string at the workflow stage,
   so GALAXY_DEV_GAME_STATE_DIR became `/.galaxy-dev/game-state`.
   Resolve in the shell instead of YAML.

2. The compose bind-mount of GeoIP2-Country-Test.mmdb referenced a
   path inside the runner's workspace volume, which the host Docker
   daemon cannot see — it created an empty directory and the backend
   crashed with "geoip database: is a directory" in a restart loop.
   Bake the file into the backend image so dev-deploy no longer needs
   a bind-mount; local-dev compose still mounts it on top for swap-in
   during development.

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

tools/dev-deploy/docker-compose.yml

@@ -125,7 +125,11 @@ services:
         target: ${GALAXY_DEV_GAME_STATE_DIR}
         bind:
           create_host_path: true
-      - ../../pkg/geoip/test-data/test-data/GeoIP2-Country-Test.mmdb:/var/lib/galaxy/geoip.mmdb:ro
+      # The GeoIP database is baked into the backend image (see
+      # tools/local-dev/backend.Dockerfile); a bind-mount is not used
+      # here because the source path resolves inside the runner
+      # workspace volume and the host Docker daemon cannot see it,
+      # which produced an "is a directory" error in CI.
     networks:
       - galaxy-internal
     healthcheck: