Stage 9: CI build on a self-hosted Gitea runner (0.7.0)

- .gitea/workflows/build.yml builds the packages and both ISOs with
  `make iso iso-server` on pushes to main and dev, v* tags and on demand
- ci/runner: setup of the CI host (WSL2 Ubuntu 24.04 with Docker Engine
  and gitea-runner as a systemd service, autostart task for Windows)
- scripts/builder.sh: DASOS_OUT keeps out/ outside the checkout, so CI
  reuses void-packages, the masterdir and the download cache
- README and TODO updated

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

VERSION

@@ -1 +1 @@
-0.6.0
+0.7.0