feat: implement light and dark theme (#30)

packages/bolt/app/components/ui/PanelHeader.tsx

@@ -8,7 +8,12 @@ interface PanelHeaderProps {
 
 export const PanelHeader = memo(({ className, children }: PanelHeaderProps) => {
   return (
-    <div className={classNames('flex items-center gap-2 bg-gray-50 border-b px-4 py-1 min-h-[34px]', className)}>
+    <div
+      className={classNames(
+        'flex items-center gap-2 bg-bolt-elements-background-depth-2 text-bolt-elements-textSecondary border-b border-bolt-elements-borderColor px-4 py-1 min-h-[34px] text-sm',
+        className,
+      )}
+    >
       {children}
     </div>
   );