Run pool-coordinator migrations automatically on container startup

[chrystianmartins]

Motivation

• Ensure the database schema is applied before the app starts to avoid runtime errors like psycopg.errors.UndefinedTable: relation "users" does not exist, and remove the obsolete top-level version key warning in the compose file.

Description

• Removed the top-level version key from docker-compose.yml and updated the pool-coordinator command to run alembic upgrade head before launching uvicorn (runs pip install -e .[dev] && alembic upgrade head && uvicorn app.main:app --host 0.0.0.0 --port 8001).

Testing

• Verified the change was committed (git show --stat) and attempted to validate the compose config with docker compose config, but Docker CLI is not available in this execution environment so runtime validation could not be completed.

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Codex Task