chore: increase left nav spacing

Push the tool list further down from the logo in the left rail.

components/top-navbar.tsx

@@ -224,7 +224,7 @@ export function TopNavbar({
       </a>
 
       {/* 侧边功能区 */}
-      <div className="mt-4 flex w-full flex-1 flex-col items-center gap-3 overflow-y-auto px-2 pb-4">
+      <div className="mt-12 flex w-full flex-1 flex-col items-center gap-3 overflow-y-auto px-2 pb-4">
         {/* 工具箱1 (如果启用且有链接) */}
         {toolbox1Enabled && customLinks.filter(l => (l.toolboxGroup || 1) === 1).length > 0 && (
           <DropdownMenu>