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_naming.py

@@ -1,5 +1,6 @@
 """ASCII-slug naming (no spaces, no accents) for on-disk paths and served filenames, and the
 social engagement-prefix strip in title normalization."""
+
 from app.downloads import storage
 from app.titles import normalize_title
 
@@ -11,7 +12,9 @@ def _is_ascii_slug(s: str) -> bool:
 def test_sanitize_folds_accents_to_ascii():
     assert storage.sanitize("Barnabás Skriván") == "Barnabas_Skrivan"
     assert storage.sanitize("Comedy Central Magyarország") == "Comedy_Central_Magyarorszag"
-    assert storage.sanitize("Marco Mobili Bútoráruház Veszprém") == "Marco_Mobili_Butoraruhaz_Veszprem"
+    assert (
+        storage.sanitize("Marco Mobili Bútoráruház Veszprém") == "Marco_Mobili_Butoraruhaz_Veszprem"
+    )
     # Hungarian double-acute (ő/ű) and German ß.
     assert storage.sanitize("Előző Műsor") == "Elozo_Musor"
     assert storage.sanitize("Straße") == "Strasse"
@@ -61,9 +64,10 @@ def test_rel_path_strips_exclamation_and_other_shell_chars():
 
 
 def test_engagement_prefix_stripped():
-    assert normalize_title(
-        "1.6M views · 66K reactions | Amikor a férfi éhesen ér haza"
-    ) == "Amikor a férfi éhesen ér haza"
+    assert (
+        normalize_title("1.6M views · 66K reactions | Amikor a férfi éhesen ér haza")
+        == "Amikor a férfi éhesen ér haza"
+    )
     assert normalize_title("13M views · 162K reactions |Valami cím") == "Valami cím"
     assert normalize_title("500 views | Rövid") == "Rövid"