feat: 添加 Gitee 按钮、关于弹框，版本号改为 v0.1.0

- 工具栏右侧新增 Gitee 图标按钮，点击跳转项目主页
- 工具栏右侧新增关于按钮，点击打开关于弹框
- 关于弹框展示：应用图标、版本号、功能特性、技术栈、版权信息
- 点击弹框外部或关闭按钮可关闭弹框
- 版本号从 v2.0.0 改为 v0.1.0

src/renderer/components/Toolbar/Toolbar.tsx

@@ -1,5 +1,5 @@
 import React from 'react'
-import { FolderOpen, Save, EditMode, PreviewMode, Moon, Sun } from '../Icons'
+import { FolderOpen, Save, EditMode, PreviewMode, Moon, Sun, Gitee, Info } from '../Icons'
 
 interface ToolbarProps {
   onOpen: () => void
@@ -8,9 +8,18 @@ interface ToolbarProps {
   onViewModeChange: (mode: 'editor' | 'preview') => void
   darkMode: boolean
   onToggleDark: () => void
+  onShowAbout: () => void
 }
 
-export function Toolbar({ onOpen, onSave, viewMode, onViewModeChange, darkMode, onToggleDark }: 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">
@@ -36,6 +45,12 @@ 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>
       </div>
     </div>
   )