Update theme and styles

- Updated the footer layout in `footer.html` to streamline the structure and improve readability.
- Added new CSS classes for brightness and invert filters in `style.css` to enhance image visibility.
- Modified the CSS source map in `custom.css.map` for better debugging.
- Changed theme name in `theme.toml` from "Hugo Saasify" to "Theme Chill" for branding consistency.

assets/scss/custom.scss

@@ -104,7 +104,7 @@ header.header {
     background-color: $bg-dark-blue;
 }
 footer.footer {
-    background-color: $chill-green;
+    background-color: $bg-dark-blue;
 }
 
 .chill-pres {