feat(design): add design scheme support and UI improvements

- Implement design scheme system with palette, typography, and feature customization
- Add color scheme dialog for user customization
- Update chat UI components to use design scheme values
- Improve header actions with consolidated deploy and export buttons
- Adjust layout spacing and styling across multiple components (chat, workbench etc...)
- Add model and provider info to chat messages
- Refactor workbench and sidebar components for better responsiveness

app/components/sidebar/Menu.client.tsx

@@ -279,8 +279,8 @@ export const Menu = () => {
   }, [open, selectionMode]);
 
   useEffect(() => {
-    const enterThreshold = 40;
-    const exitThreshold = 40;
+    const enterThreshold = 20;
+    const exitThreshold = 20;
 
     function onMouseMove(event: MouseEvent) {
       if (isSettingsOpen) {
@@ -331,13 +331,13 @@ export const Menu = () => {
         variants={menuVariants}
         style={{ width: '340px' }}
         className={classNames(
-          'flex selection-accent flex-col side-menu fixed top-0 h-full',
-          'bg-white dark:bg-gray-950 border-r border-gray-100 dark:border-gray-800/50',
+          'flex selection-accent flex-col side-menu fixed top-0 h-full rounded-r-2xl',
+          'bg-white dark:bg-gray-950 border-r border-bolt-elements-borderColor',
           'shadow-sm text-sm',
           isSettingsOpen ? 'z-40' : 'z-sidebar',
         )}
       >
-        <div className="h-12 flex items-center justify-between px-4 border-b border-gray-100 dark:border-gray-800/50 bg-gray-50/50 dark:bg-gray-900/50">
+        <div className="h-12 flex items-center justify-between px-4 border-b border-gray-100 dark:border-gray-800/50 bg-gray-50/50 dark:bg-gray-900/50 rounded-tr-2xl">
           <div className="text-gray-900 dark:text-white font-medium"></div>
           <div className="flex items-center gap-3">
             <span className="font-medium text-sm text-gray-900 dark:text-white truncate">