feat(EditorPanel): Add save button to editor toolbar

- Add primary save button with SaveOutlined icon to editor toolbar
- Implement onClick handler for document saving functionality
- Display loading state during save operation
- Add tooltip text "保存文档" for better UX
- Position save button between export and divider for logical flow
- Improve document management workflow by providing direct save action

src/components/EditorPanel/EditorPanel.tsx

@@ -251,6 +251,16 @@ export const EditorPanel: React.FC<EditorPanelProps> = ({
           >
             导出
           </Button>
+          <Button
+            type="primary"
+            size="small"
+            icon={<SaveOutlined />}
+            onClick={handleSave}
+            loading={saving}
+            title="保存文档"
+          >
+            保存
+          </Button>
           <Divider type="vertical" style={{ margin: '0 4px' }} />
           <Button
             type="text"