refactor: 移除工具栏 Gitee 按钮，项目地址移至关于弹框

- 工具栏移除 Gitee 图标按钮
- 关于弹框添加项目地址链接（带 Gitee 图标）
- 链接点击跳转到 gitee.com/thzxx/MarkLite

src/renderer/components/Toolbar/Toolbar.tsx

@@ -1,5 +1,5 @@
 import React from 'react'
-import { FolderOpen, Save, EditMode, PreviewMode, Moon, Sun, Gitee, Info } from '../Icons'
+import { FolderOpen, Save, EditMode, PreviewMode, Moon, Sun, Info } from '../Icons'
 
 interface ToolbarProps {
   onOpen: () => void
@@ -12,14 +12,6 @@ interface ToolbarProps {
 }
 
 export function Toolbar({ onOpen, onSave, viewMode, onViewModeChange, darkMode, onToggleDark, onShowAbout }: ToolbarProps) {
-  const handleOpenGitee = () => {
-    if (window.electronAPI?.openExternal) {
-      window.electronAPI.openExternal('https://gitee.com/thzxx/MarkLite')
-    } else {
-      window.open('https://gitee.com/thzxx/MarkLite', '_blank')
-    }
-  }
-
   return (
     <div id="toolbar">
       <div className="toolbar-left">
@@ -45,9 +37,6 @@ export function Toolbar({ onOpen, onSave, viewMode, onViewModeChange, darkMode,
         <button className="toolbar-btn" onClick={onToggleDark} title="切换暗色主题">
           {darkMode ? <Sun size={18} /> : <Moon size={18} />}
         </button>
-        <button className="toolbar-btn" onClick={handleOpenGitee} title="Gitee 项目主页">
-          <Gitee size={18} />
-        </button>
         <button className="toolbar-btn" onClick={onShowAbout} title="关于">
           <Info size={18} />
         </button>