Replace the fleet's in-runtime auto-updater with a git-driven update-tracking system

The Raspberry Pi and NAS device fleet previously relied on an in-runtime auto-updater that could fail partway through a pull and leave an application stopped with no retry and no alert.

Replaced with a fully git-driven design: a dependency-update bot proposes new versions in source control, the existing container-management platform performs the actual redeploy using its own tested logic, and a read-only watcher confirms the update actually landed and posts a notification if it doesn't.

Both the platform's own version and the fleet's management agents are now tracked in git and kept current on a documented, repeatable process.