Crash recovery (check_for_crash + recover_containers +
start_stopped_containers) now runs in a background tokio task.
The health endpoint is available immediately on startup instead of
blocking for 260+ seconds while containers restart sequentially.
This directly fixes the .198 boot recovery timeout issue where the
backend took 260s to become healthy after restart.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>