feat: add console install command

[nichenqin]

Summary

• add command=install-console to install or upgrade a self-hosted Appaloft console over SSH
• support console origin/domain, database, HTTP bind, image, installer URL, and Docker install policy inputs
• keep deploy and preview-cleanup behavior separate from console installation

Verification

• bash -n scripts/install-appaloft.sh scripts/run-deploy.sh scripts/resolve-control-plane.sh
• dry-run command=install-console smoke

[nichenqin]

Closing this stacked PR in favor of #9, which syncs the complete self-host console bootstrap wrapper from appaloft/appaloft#203 in one PR.