refactor: remove CSS variables from Range.scss for cleaner styling

- Eliminated default CSS variables for slider and range track styles from Range.scss to streamline the styling process.
- Added appearance property to the range input for improved cross-browser compatibility.

Author: atyrode

src/frontend/src/ui/Range.scss

@@ -1,10 +1,3 @@
-:root {
-  --slider-thumb-size: 16px;
-  --range-track-filled: #cc6d24;
-  --range-track-unfilled: #525252;
-  --range-thumb-color: #a4571b; /* Slightly lighter than track-filled for contrast */
-}
-
 .range {
   &__control-label {
     display: flex;
@@ -25,6 +18,7 @@
     width: 100%;
     height: 4px;
     -webkit-appearance: none;
+    appearance: none;
     background: var(--range-track-filled);
     border-radius: 2px;
     outline: none;