Add a --kill flag (-k) to the `astro dev restart` command that kills all
running containers and removes all data before restarting. This allows users
to run `astro dev restart --kill` instead of having to run `astro dev kill &&
astro dev start` separately.

When the --kill flag is used, the command calls containerHandler.Kill()
instead of containerHandler.Stop(true), which permanently deletes all
container data before starting fresh.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>