feat(widgets): user-card guest OAuth social login bar

Match zibll widget_ui_user guest shell with social provider buttons
under login/register CTAs.

assets/css/frontend/widget-batch5.css

@@ -512,3 +512,18 @@
   color: var(--muted-2-color, #999);
   font-size: 12px;
 }
+
+.aksrt-user-card__oauth {
+  margin-top: 14px;
+  padding-top: 12px;
+  border-top: 1px dashed var(--color-line, #e5e7eb);
+}
+.aksrt-user-card__oauth .social-login-divider {
+  font-size: 12px;
+  color: var(--muted-2-color, #999);
+  margin-bottom: 8px;
+}
+.aksrt-user-card__oauth .social-login-item,
+.aksrt-user-card__oauth a {
+  margin: 0 4px;
+}

src/AKSRT/Widgets/WidgetUserCard.php

@@ -137,6 +137,16 @@ class WidgetUserCard extends \WP_Widget {
 			? get_avatar_url(0, ['size' => 144, 'force_default' => true])
 			: includes_url('images/blank.gif');
 
+		$oauth_html = '';
+		if (class_exists('\AKSRT\Auth\OAuth')) {
+			$oauth = \AKSRT\Auth\OAuth::get_instance();
+			if (method_exists($oauth, 'render_social_buttons')) {
+				$oauth_html = (string) $oauth->render_social_buttons(__('社交账号登录', 'aksrt'));
+			} elseif (method_exists($oauth, 'get_login_buttons')) {
+				$oauth_html = (string) $oauth->get_login_buttons();
+			}
+		}
+
 		echo '<div class="aksrt-user-card user-card zib-widget widget is-guest">';
 		if ($show_cover) {
 			echo '<div class="aksrt-user-card__cover user-cover graphic is-empty"></div>';
@@ -147,9 +157,13 @@ class WidgetUserCard extends \WP_Widget {
 		echo '<div class="aksrt-user-card__actions">';
 		echo '<a class="aksrt-user-card__btn aksrt-user-card__btn--primary signin-loader" href="' . esc_url($login) . '">' . esc_html__('登录', 'aksrt') . '</a>';
 		if ($register) {
-			echo '<a class="aksrt-user-card__btn aksrt-user-card__btn--ghost" href="' . esc_url($register) . '">' . esc_html__('注册', 'aksrt') . '</a>';
+			echo '<a class="aksrt-user-card__btn aksrt-user-card__btn--ghost signup-loader" href="' . esc_url($register) . '">' . esc_html__('注册', 'aksrt') . '</a>';
 		}
-		echo '</div></div></div>';
+		echo '</div>';
+		if ($oauth_html !== '') {
+			echo '<div class="aksrt-user-card__oauth social_loginbar">' . $oauth_html . '</div>'; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
+		}
+		echo '</div></div>';
 	}
 
 	public function form($instance): void {