feat(nav.scss): add styles for navigation bar

- Added styles for the navigation bar to improve the appearance and functionality of the navigation component.
- The navigation bar now has a fixed position at the bottom of the screen and is displayed as a flex container with space between and aligned center.
- The width of the navigation bar is set to 100% and the height is set using a CSS variable (--nav-height).
- Added padding to the navigation bar for spacing.
- The navigation bar has a white background and a z-index value of (--z-nav) to ensure it appears above other elements.
- The pointer-events property is set to "all" to maintain functionality while the container is locked.
- Added styles for the ".num" and ".current" classes.
- Added media queries to adjust the position and visibility of the navigation bar on smaller screens or devices without hover capability.

assets/scss/_partial/_nav.scss

@@ -34,7 +34,6 @@ nav {
 @media (max-width: $tablet), (hover: none) {
   nav {
     top: 0;
-    position: sticky;
   }
 
   .index,