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_og.py

@@ -3,6 +3,7 @@
 Facebook's scraper fetches og:image asynchronously on first scrape, so the card is image-less
 unless og:image:width/height are declared — which needs the poster's real dimensions, read from the
 JPEG header without an image library. This pins that parser."""
+
 import struct
 
 from app.downloads.og import _jpeg_size