Add Docker support with Dockerfile, entrypoint script, and CI workflows

- Introduced a Dockerfile for building the application with Go and Node.js dependencies.
- Added a docker-entrypoint.sh script to manage container execution.
- Created a .dockerignore file to exclude unnecessary files from the Docker context.
- Updated Makefile to include a new target for building the Docker image.
- Added CI workflows for testing, formatting, and releasing artifacts in Gitea.

docker-entrypoint.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+set -eu
+
+# Default to running the server with mounted config.
+if [ "$#" -eq 0 ]; then
+  set -- server --config /config/config.yaml
+elif [ "${1#-}" != "$1" ]; then
+  # Allow passing server flags directly, e.g. `docker run ... --config ...`.
+  set -- server "$@"
+fi
+
+exec scratchbox "$@"