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_security.py

@@ -5,6 +5,7 @@ the token-at-rest path (Google/API/SMTP/Plex secrets in system_config, OAuth ref
 Fernet key is monkeypatched in so the test doesn't depend on TOKEN_ENCRYPTION_KEY being set in the env.
 Pure-logic (no DB).
 """
+
 from cryptography.fernet import Fernet
 
 from app import security