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/progress.py

@@ -6,6 +6,7 @@ holds the sink, so the sync code stays unaware of the scheduler and concurrent j
 its own thread/context) never cross wires. When no sink is bound (e.g. a manual sync endpoint),
 `report` is a cheap no-op.
 """
+
 import contextvars
 from typing import Callable, Optional