importers: manifest + audit log on --force rmtree
Build a per-file SHA-256 manifest before shutil.rmtree in
_setup_import's --force branch and append an
import_force_reimport entry via log_app_action. Thread
dry_run through so --force --dry-run logs the would-be-deleted
manifest without touching imports/.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>