🐛 | Fix SonarQube issues

- Extract duplicated string literals into constants (S1192)
- Replace dict() with {} literal (S7498)
- Remove duplicate test_zero_ms (S4144)
- Remove/rename unused variables (S1481)
- Replace constant assert True with comment (S5914)
- Mark stub empty methods as intentional (S1186)
- Review 2 security hotspots as safe (S5443)

tests/test_player_helpers.py

@@ -239,8 +239,8 @@ class TestStaleFiles:
         td = tempfile.mkdtemp(prefix="tunetti_test_")
         monkeypatch.setattr("player._TUNETTI_TMP", td)
 
-        with open(os.path.join(td, "vid123.mp3"), "w") as f:
-            pass  # empty
+        with open(os.path.join(td, "vid123.mp3"), "w") as _f:
+            pass  # empty; _f unused intentionally
 
         result = _stale_files("vid123")
         assert result == []