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_request_models.py

@@ -1,6 +1,7 @@
 """R6 S1b: the request models turn payloads that used to 500 into clean validation errors,
 and PATCH models distinguish an absent field from an explicit null. Pure-logic (no DB) — it
 exercises the Pydantic models the route modules define, not the endpoints."""
+
 import pytest
 from pydantic import ValidationError
 
@@ -13,6 +14,7 @@ from app.routes.tags import TagUpdateIn
 
 # --- The three ROADMAP-named 500-producers are now 422s (ValidationError at the boundary). ---
 
+
 def test_channel_priority_rejects_non_numeric():
     # Was `int(payload["priority"])` → 500 on garbage. Now a validation error.
     with pytest.raises(ValidationError):
@@ -58,6 +60,7 @@ def test_progress_accepts_fractional_seconds():
 
 # --- PATCH models: model_fields_set separates "absent" from "explicit null". ---
 
+
 def test_tag_update_absent_vs_null_color():
     absent = TagUpdateIn()
     assert "color" not in absent.model_fields_set  # untouched on PATCH