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.

README.md

@@ -21,13 +21,18 @@ A range of features are implemented to support these functionalities.
 - **Unified UI Shell**: Server-rendered templates extend a shared base layout with a persistent left sidebar linking scenarios, parameters, costs, consumption, production, equipment, maintenance, simulations, and reporting views.
 - **Operations Overview Dashboard**: The root route (`/`) surfaces cross-scenario KPIs, charts, and maintenance reminders with a one-click refresh backed by aggregated loaders.
 - **Theming Tokens**: Shared CSS variables in `static/css/main.css` centralize the UI color palette for consistent styling and rapid theme tweaks.
-- **Modular Frontend Scripts**: Page-specific interactions now live in `static/js/` modules, keeping templates lean while enabling browser caching and reuse.
+- **Settings Center**: The Settings landing page exposes visual theme controls and links to currency administration, backed by persisted application settings and environment overrides.
+- **Modular Frontend Scripts**: Page-specific interactions in `static/js/` modules, keeping templates lean while enabling browser caching and reuse.
 - **Monte Carlo Simulation (in progress)**: Services and routes are scaffolded for future stochastic analysis.
 
 ## Documentation & quickstart
 
 This repository contains detailed developer and architecture documentation in the `docs/` folder.
 
+### Settings overview
+
+The Settings page (`/ui/settings`) lets administrators adjust global theme colors stored in the `application_setting` table. Changes are instantly applied across the UI. Environment variables prefixed with `CALMINER_THEME_` (for example, `CALMINER_THEME_COLOR_PRIMARY`) automatically override individual CSS variables and render as read-only in the form, ensuring deployment-time overrides take precedence while remaining visible to operators.
+
 [Quickstart](docs/quickstart.md) contains developer quickstart, migrations, testing and current status.
 
 Key architecture documents: see [architecture](docs/architecture/README.md) for the arc42-based architecture documentation.