Evolve domains from project issue signals

Hive now lets domain evolution grow organically from the work signals on a project. GitHub issue syncing polls every repository attached to a project, so a manually created project can start producing issue signals even when no domains exist yet. When the evolution agent proposes a new domain, it can supply project identifiers and Hive validates and links the created domain back to those projects. Existing domain classification and project links continue to work unchanged, and no database migration is required. The self-hosting agents guide now documents GitHub issues and Grafana alerts as domain evolution signals.