Add Dark Mode Support to Harbor Website

[mythicalyash]

Description
The Harbor website currently only supports a light theme, which can be uncomfortable for users who prefer dark mode or work in low-light environments. This issue proposes adding a dark mode feature with the following capabilities:

Proposed Features

Theme Toggle: A user-friendly toggle button in the navbar to switch between light and dark modes
System Preference Detection: Automatically detect and respect the user's system theme preference (prefers-color-scheme)
Persistent Selection: Remember the user's theme choice across sessions using localStorage
FOUC Prevention: Implement inline script to prevent Flash of Unstyled Content on page load
Comprehensive Styling: Ensure all components (navbar, footer, cards, tables, code blocks, etc.) are properly styled for dark mode
Benefits
Improved Accessibility: Better readability for users with light sensitivity or those working in dark environments
Modern UX: Aligns with current web design trends and user expectations
User Preference: Respects system-level theme preferences while allowing manual override

[mythicalyash]

@bupd
I already implemented dark mode
and opened a pull request
Please assign this task to me

[mythicalyash]

#703