fix: allow Docker Compose commands from subdirectories

[vitormattos]

Description

Docker Compose can find docker-compose.yml by searching parent directories, but the proxy-coordinator was using ${PWD} as the project directory.

Because ${PWD} is the directory where the command is executed, running docker compose from a subdirectory made the coordinator use the wrong project path.

This PR:

• mounts the project at a fixed /project path inside the coordinator;
• uses /project as PROJECT_DIR and the coordinator working directory;
• copies proxy assets through stdin instead of passing the coordinator path as a host bind mount to the Docker daemon;
• adds a CI check that compares docker compose config from the repository root and from .docker.

This keeps the Compose configuration independent from the directory where the developer runs the command.