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/realtime.py

@@ -11,6 +11,7 @@ they schedule the actual send onto the WebSocket event loop via run_coroutine_th
 connect/disconnect/_push coroutines all run on that one loop, so the connection map is only ever
 mutated from a single thread.
 """
+
 import asyncio
 import logging
 from collections import defaultdict