feat(auth): 登录页改为 ymb 品牌并支持后台配置背景图

test/config/server_endpoint_test.dart

@@ -74,6 +74,7 @@ void main() {
     final prod = Uri.parse(ProdConfig.baseUrl);
 
     expect(dev.scheme, 'http');
+    expect(dev.host, isNot(prod.host));
     expect(dev.port, 8081);
     expect(dev.path, isEmpty);
     expect(prod.scheme, 'http');