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/tests/test_search_scrape_ingest.py

@@ -10,6 +10,7 @@ The stub now falls back to now() (a non-null placeholder), and the enrich overwr
 video's real snippet date. These DB-lane tests lock both halves: no crash on a date-less stub, and
 a placeholder never becomes the video's permanent date.
 """
+
 from datetime import datetime, timezone
 
 from app import sysconfig