style: apply ruff format across backend + scripts (line-length 100)

Mechanical, whole-tree `ruff format` pass — no behaviour change. Recorded in
.git-blame-ignore-revs (next commit) so git blame skips it.

backend/app/audit.py

@@ -9,6 +9,7 @@ runs are always logged. Secrets are never stored (config changes log the key nam
 mutation it describes, so the trail can't drift from reality (and a rolled-back mutation drops
 its audit row too).
 """
+
 from datetime import datetime, timedelta, timezone
 
 from sqlalchemy import delete