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_ui_routes.py

@@ -21,11 +21,18 @@ def test_dashboard_route_provides_summary(
     assert context.get("report_available") is True
 
     metric_labels = {item["label"] for item in context["summary_metrics"]}
-    assert {"CAPEX Total", "OPEX Total", "Production", "Simulation Iterations"}.issubset(metric_labels)
+    assert {
+        "CAPEX Total",
+        "OPEX Total",
+        "Production",
+        "Simulation Iterations",
+    }.issubset(metric_labels)
 
     scenario = cast(Scenario, seeded_ui_data["scenario"])
     scenario_row = next(
-        row for row in context["scenario_rows"] if row["scenario_name"] == scenario.name
+        row
+        for row in context["scenario_rows"]
+        if row["scenario_name"] == scenario.name
     )
     assert scenario_row["iterations"] == 3
     assert scenario_row["simulation_mean_display"] == "971,666.67"
@@ -81,7 +88,9 @@ def test_dashboard_data_endpoint_returns_aggregates(
     payload = response.json()
     assert payload["report_available"] is True
 
-    metric_map = {item["label"]: item["value"] for item in payload["summary_metrics"]}
+    metric_map = {
+        item["label"]: item["value"] for item in payload["summary_metrics"]
+    }
     assert metric_map["CAPEX Total"].startswith("$")
     assert metric_map["Maintenance Cost"].startswith("$")
 
@@ -99,7 +108,9 @@ def test_dashboard_data_endpoint_returns_aggregates(
 
     activity_labels = payload["scenario_activity_chart"]["labels"]
     activity_idx = activity_labels.index(scenario.name)
-    assert payload["scenario_activity_chart"]["production"][activity_idx] == 800.0
+    assert (
+        payload["scenario_activity_chart"]["production"][activity_idx] == 800.0
+    )
 
 
 @pytest.mark.parametrize(
@@ -154,7 +165,10 @@ def test_settings_route_provides_css_context(
     assert "css_env_override_meta" in context
 
     assert context["css_variables"]["--color-accent"] == "#abcdef"
-    assert context["css_defaults"]["--color-accent"] == settings_service.CSS_COLOR_DEFAULTS["--color-accent"]
+    assert (
+        context["css_defaults"]["--color-accent"]
+        == settings_service.CSS_COLOR_DEFAULTS["--color-accent"]
+    )
     assert context["css_env_overrides"]["--color-accent"] == "#abcdef"
 
     override_rows = context["css_env_override_rows"]