Add dark mode support across the UI

What problem are you trying to solve?

When using the interface in low-light environments or during extended work sessions, the current bright default theme causes significant eye strain and fatigue. There is currently no option to switch to a dark theme or automatically match the system preference.

Describe the solution you'd like

Introduce a native Dark Mode toggle in the application settings, alongside an option to automatically synchronize with the operating system's theme preference (System Default / Light / Dark). Ensure all core UI components, text elements, and background contrast levels conform to dark theme accessibility standards.

Alternatives you've considered

Non

Additional context

Additional context Adding a dark mode will improve user comfort during night use and reduce device battery consumption on OLED displays.

Would you be willing to contribute a PR?

Yes, I can take this on