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/styles/global.css

@@ -1081,3 +1081,110 @@ html, body {
   from { opacity: 0; transform: translateY(8px); }
   to { opacity: 1; transform: translateY(0); }
 }
+
+/* About Dialog */
+.about-overlay {
+  position: fixed;
+  top: 0;
+  left: 0;
+  right: 0;
+  bottom: 0;
+  background: rgba(0, 0, 0, 0.5);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  z-index: 10000;
+  animation: fadeIn 0.2s ease;
+}
+
+.about-dialog {
+  background: var(--bg);
+  border-radius: 12px;
+  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.2);
+  padding: 32px;
+  width: 360px;
+  max-width: 90vw;
+  text-align: center;
+  animation: fadeIn 0.2s ease;
+}
+
+.about-header {
+  margin-bottom: 20px;
+}
+
+.about-header h2 {
+  margin: 12px 0 4px;
+  font-size: 24px;
+  font-weight: 600;
+  color: var(--text);
+}
+
+.about-version {
+  display: inline-block;
+  background: var(--primary-light);
+  color: var(--primary);
+  padding: 2px 10px;
+  border-radius: 12px;
+  font-size: 13px;
+  font-weight: 500;
+}
+
+.about-body {
+  margin-bottom: 20px;
+}
+
+.about-body > p {
+  color: var(--text-secondary);
+  font-size: 14px;
+  margin-bottom: 16px;
+}
+
+.about-features {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 8px;
+  justify-content: center;
+}
+
+.about-features span {
+  background: var(--bg-secondary);
+  color: var(--text-secondary);
+  padding: 4px 12px;
+  border-radius: 6px;
+  font-size: 12px;
+  border: 1px solid var(--border-light);
+}
+
+.about-footer {
+  padding-top: 16px;
+  border-top: 1px solid var(--border-light);
+  margin-bottom: 20px;
+}
+
+.about-footer p {
+  color: var(--text-tertiary);
+  font-size: 12px;
+  margin: 4px 0;
+}
+
+.about-copyright {
+  font-weight: 500;
+}
+
+.about-close-btn {
+  width: 100%;
+  padding: 10px;
+  background: var(--primary);
+  color: white;
+  border: none;
+  border-radius: 8px;
+  font-size: 14px;
+  font-family: var(--font-ui);
+  font-weight: 500;
+  cursor: pointer;
+  transition: background 0.15s ease;
+}
+
+.about-close-btn:hover {
+  background: var(--primary-dark);
+}