fix: sidebar polish — logo, scrollbar, utility bar height, icon flash

- Fix stretched logo with object-contain
- Remove border below logo
- Add overflow-hidden to prevent scrollbar flash during transition
- Match utility bar height to old header (py-3.5)
- Remove transition-colors from active nav items to prevent white flash

components/dashboard/UtilityBar.tsx

@@ -67,7 +67,7 @@ export default function UtilityBar() {
   }
 
   return (
-    <div className="shrink-0 flex items-center justify-between border-b border-neutral-200 dark:border-neutral-800 bg-white dark:bg-neutral-900 px-4 sm:px-6 py-2">
+    <div className="shrink-0 flex items-center justify-between border-b border-neutral-200 dark:border-neutral-800 bg-white dark:bg-neutral-900 px-4 sm:px-8 py-3.5">
       {/* Left: mobile sidebar toggle */}
       <button
         onClick={openMobile}