chore: remove deprecated docker-compose version field

Remove deprecated 'version' field from docker-compose.dev.yml.
Docker Compose v2 ignores this field and it's no longer needed.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[e-mail]>

docker-compose.dev.yml

···
-version: '3.8'
-
 # Coves Local Development Stack
 # All-in-one setup: PDS + PostgreSQL + optional Relay
 #