feat: update button variants and styles for improved consistency and accessibility

src/components/user/theme-picker.tsx

@@ -18,7 +18,7 @@ export function ThemePicker() {
   return (
     <DropdownMenu>
       <DropdownMenuTrigger asChild>
-        <Button variant='outline' size='icon'>
+        <Button variant='outline_primary' size='icon'>
           <Sun className='h-[1.2rem] w-[1.2rem] rotate-0 scale-100 transition-all dark:-rotate-90 dark:scale-0' />
           <Moon className='absolute h-[1.2rem] w-[1.2rem] rotate-90 scale-0 transition-all dark:rotate-0 dark:scale-100' />
           <span className='sr-only'>Toggle theme</span>