Implement dark mode

### User Story

As a user, I want the option to switch to a dark mode in our web application to reduce eye strain and improve readability, especially in low-light environments.

### Description

Implementing a dark mode for our web application involves creating a new color scheme and adjusting the styles of various components to ensure readability and usability in dark mode. This task will primarily focus on updating the design and CSS to support a dark theme.

### Acceptance Criteria

- [ ] Design a dark color scheme that is visually appealing and aligns with our brand.
- [ ] Update CSS styles to support the dark theme, including text colors, background colors, and contrast ratios.
- [ ] Ensure that all components are easily readable and accessible in dark mode.
- [ ] Implement a toggle or setting in the application to switch between light and dark modes.
- [ ] Test the dark mode across different browsers and devices to ensure consistent rendering and usability.