feat: add CI/CD workflow and switch to bind mount for data

Use a Gitea Actions workflow to deploy on push to main via
act_runner on the games VM. Switch from a Docker named volume
to a ./data bind mount for easier backup and persistence across
deploys.

docker-compose.yml

@@ -11,7 +11,4 @@ services:
     environment:
       - PORT=8080
     volumes:
-      - c4-data:/app/data
-
-volumes:
-  c4-data:
+      - ./data:/app/data