fix(docker): stop ignoring entrypoint.sh

.dockerignore excluded entrypoint.sh while the Dockerfile COPYs it into
the runtime stage; buildx (docker-container driver) fails hard on this
where the legacy builder only warned.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.dockerignore

@@ -17,7 +17,6 @@ macos/
 *.log
 Dockerfile
 docker-compose.yml
-entrypoint.sh
 README.md
 task.md
 implementation_plan.md