Refactor test cases for improved readability and consistency

- Updated test functions in various test files to enhance code clarity by formatting long lines and improving indentation.
- Adjusted assertions to use multi-line formatting for better readability.
- Added new test cases for theme settings API to ensure proper functionality.
- Ensured consistent use of line breaks and spacing across test files for uniformity.

tests/unit/test_settings_service.py

@@ -20,8 +20,14 @@ def fixture_clean_env(monkeypatch: pytest.MonkeyPatch) -> Dict[str, str]:
 
 
 def test_css_key_to_env_var_formatting():
-    assert settings_service.css_key_to_env_var("--color-background") == "CALMINER_THEME_COLOR_BACKGROUND"
-    assert settings_service.css_key_to_env_var("--color-primary-stronger") == "CALMINER_THEME_COLOR_PRIMARY_STRONGER"
+    assert (
+        settings_service.css_key_to_env_var("--color-background")
+        == "CALMINER_THEME_COLOR_BACKGROUND"
+    )
+    assert (
+        settings_service.css_key_to_env_var("--color-primary-stronger")
+        == "CALMINER_THEME_COLOR_PRIMARY_STRONGER"
+    )
 
 
 @pytest.mark.parametrize(
@@ -33,7 +39,9 @@ def test_css_key_to_env_var_formatting():
         ("--color-text-secondary", "hsla(210, 40%, 40%, 1)"),
     ],
 )
-def test_read_css_color_env_overrides_valid_values(clean_env, env_key, env_value):
+def test_read_css_color_env_overrides_valid_values(
+    clean_env, env_key, env_value
+):
     env_var = settings_service.css_key_to_env_var(env_key)
     clean_env[env_var] = env_value
 
@@ -50,7 +58,9 @@ def test_read_css_color_env_overrides_valid_values(clean_env, env_key, env_value
         "rgb(1,2)",  # malformed rgb
     ],
 )
-def test_read_css_color_env_overrides_invalid_values_raise(clean_env, invalid_value):
+def test_read_css_color_env_overrides_invalid_values_raise(
+    clean_env, invalid_value
+):
     env_var = settings_service.css_key_to_env_var("--color-background")
     clean_env[env_var] = invalid_value
 
@@ -64,7 +74,9 @@ def test_read_css_color_env_overrides_ignores_missing(clean_env):
 
 
 def test_list_css_env_override_rows_returns_structured_data(clean_env):
-    clean_env[settings_service.css_key_to_env_var("--color-primary")] = "#123456"
+    clean_env[settings_service.css_key_to_env_var("--color-primary")] = (
+        "#123456"
+    )
     rows = settings_service.list_css_env_override_rows(clean_env)
     assert rows == [
         {