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_feed_cursor.py

@@ -5,6 +5,7 @@ plain ValueError and routes/feed.get_feed translates it to 400 — so a future r
 try/except, or a new decode_cursor caller without its own catch) turns the 400 back into a 500 and
 fails right here. DB lane (`db` fixture) — skipped without Postgres.
 """
+
 from fastapi.testclient import TestClient
 
 import app.state as state
@@ -15,7 +16,9 @@ from app.models import User
 
 
 def _get(db, user, monkeypatch, path):
-    monkeypatch.setattr(state, "_configured_cache", True)  # the request gate 503s an unconfigured app
+    monkeypatch.setattr(
+        state, "_configured_cache", True
+    )  # the request gate 503s an unconfigured app
     app.dependency_overrides[get_db] = lambda: db
     app.dependency_overrides[current_user] = lambda: user
     try: