style: add modern-scrollbar class to improve scrollbar appearance

Introduce the modern-scrollbar class to enhance the visual consistency of scrollbars across the application. This class provides a cleaner and more modern look for scrollbars in WebKit and Firefox browsers.

app/components/workbench/terminal/TerminalTabs.tsx

@@ -150,7 +150,7 @@ export const TerminalTabs = memo(() => {
                 <Terminal
                   key={index}
                   id={`terminal_${index}`}
-                  className={classNames('h-full overflow-hidden', {
+                  className={classNames('h-full overflow-hidden modern-scrollbar-invert', {
                     hidden: !isActive,
                   })}
                   ref={(ref) => {
@@ -166,7 +166,7 @@ export const TerminalTabs = memo(() => {
                 <Terminal
                   key={index}
                   id={`terminal_${index}`}
-                  className={classNames('h-full overflow-hidden', {
+                  className={classNames('modern-scrollbar h-full overflow-hidden', {
                     hidden: !isActive,
                   })}
                   ref={(ref) => {