🐛 | 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_gui_helpers.py

@@ -34,10 +34,6 @@ class TestFmtMs:
         assert fn(3600_000) == "60:00"
         assert fn(3661_000) == "61:01"
 
-    def test_zero_ms(self):
-        fn = self._import()
-        assert fn(0) == "0:00"
-
     def test_large_duration(self):
         fn = self._import()
         assert fn(5999_000) == "99:59"