feat: Add application-level settings for CSS color management

- Introduced a new table `application_setting` to store configurable application options.
- Implemented functions to manage CSS color settings, including loading, updating, and reading environment overrides.
- Added a new settings view to render and manage theme colors.
- Updated UI to include a settings page with theme color management and environment overrides display.
- Enhanced CSS styles for the settings page and sidebar navigation.
- Created unit and end-to-end tests for the new settings functionality and CSS management.

tests/e2e/test_smoke.py

@@ -7,6 +7,7 @@ UI_ROUTES = [
     ("/ui/dashboard", "Dashboard · CalMiner", "Operations Overview"),
     ("/ui/scenarios", "Scenario Management · CalMiner", "Create a New Scenario"),
     ("/ui/parameters", "Process Parameters · CalMiner", "Scenario Parameters"),
+    ("/ui/settings", "Settings · CalMiner", "Settings"),
     ("/ui/costs", "Costs · CalMiner", "Cost Overview"),
     ("/ui/consumption", "Consumption · CalMiner", "Consumption Tracking"),
     ("/ui/production", "Production · CalMiner", "Production Output"),
@@ -27,3 +28,45 @@ def test_ui_pages_load_correctly(page: Page, url: str, title: str, heading: str)
     heading_locator = page.locator(
         f"h1:has-text('{heading}'), h2:has-text('{heading}')")
     expect(heading_locator.first).to_be_visible()
+
+
+def test_settings_theme_form_interaction(page: Page):
+    page.goto("/ui/settings")
+    expect(page).to_have_title("Settings · CalMiner")
+
+    env_rows = page.locator("#theme-env-overrides tbody tr")
+    disabled_inputs = page.locator(
+        "#theme-settings-form input.color-value-input[disabled]")
+    env_row_count = env_rows.count()
+    disabled_count = disabled_inputs.count()
+    assert disabled_count == env_row_count
+
+    color_input = page.locator(
+        "#theme-settings-form input[name='--color-primary']")
+    expect(color_input).to_be_visible()
+    expect(color_input).to_be_enabled()
+
+    original_value = color_input.input_value()
+    candidate_values = ("#114455", "#225566")
+    new_value = candidate_values[0] if original_value != candidate_values[0] else candidate_values[1]
+
+    color_input.fill(new_value)
+    page.click("#theme-settings-form button[type='submit']")
+
+    feedback = page.locator("#theme-settings-feedback")
+    expect(feedback).to_contain_text("updated successfully")
+
+    computed_color = page.evaluate(
+        "() => getComputedStyle(document.documentElement).getPropertyValue('--color-primary').trim()"
+    )
+    assert computed_color.lower() == new_value.lower()
+
+    page.reload()
+    expect(color_input).to_have_value(new_value)
+
+    color_input.fill(original_value)
+    page.click("#theme-settings-form button[type='submit']")
+    expect(feedback).to_contain_text("updated successfully")
+
+    page.reload()
+    expect(color_input).to_have_value(original_value)