fix(web): 工作区布局 - 主区账户图标默认态不再发灰

- 账户触发按钮加 app-workspace-account-trigger 类，占位 CircleUserRound 覆盖为 var(--foreground) 100%，不再套用图标按钮 58% 弱化；hover 仍保持背景反馈

web/src/components/layout/workspace-account-menu.tsx

@@ -72,7 +72,7 @@ export function WorkspaceAccountMenu() {
                 </div>
             )}
         >
-            <button type="button" className="app-workspace-topbar-icon-button" aria-label="账户菜单" title={user.displayName || user.username}>
+            <button type="button" className="app-workspace-topbar-icon-button app-workspace-account-trigger" aria-label="账户菜单" title={user.displayName || user.username}>
                 <UserAvatar user={user} className="size-6" />
             </button>
         </Popover>