fix(toolbar): adjust toolbar position to center

[jyxjjj]

Description / 描述

修复更新导致的工具栏偏移

可能修的不够优雅

Motivation and Context / 背景

How Has This Been Tested? / 测试

警告：这不是通过前端代码编译后执行的，而是直接从demo在浏览器中以相同方式进行的修改。所以还需要审查。

Checklist / 检查清单

• I have read the CONTRIBUTING document.
  我已阅读 CONTRIBUTING 文档。
• I have formatted my code with go fmt or prettier.
  我已使用 go fmt 或 prettier 格式化提交的代码。
• I have added appropriate labels to this PR (or mentioned needed labels in the description if lacking permissions).
  我已为此 PR 添加了适当的标签（如无权限或需要的标签不存在，请在描述中说明，管理员将后续处理）。
• I have requested review from relevant code authors using the "Request review" feature when applicable.
  我已在适当情况下使用"Request review"功能请求相关代码作者进行审查。

[Copilot]

Pull request overview

This PR adjusts the home page center toolbar’s fixed positioning to correct an offset introduced after a recent update, aiming to keep the toolbar visually centered at the bottom of the viewport when it appears.

Changes:

• Switch the center toolbar anchoring from right: 50% to left: 50%.
• Update Motion transform x values from "50%" to "-50%" to match the new anchoring approach.
• Include x in the exit animation state.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.