fix(user-center): replicate reference theme sidebar icons via SVG sprite

The user-center sidebar rendered Font Awesome glyphs while the reference theme
paints multi-tone inline SVGs, and several glyphs were simply wrong for their
slot: fa-chart-line served both 我的等级 and 推广收益, fa-money-bill served both
余额 and 积分, and fa-pen stood in for 创作收益.

The theme already ships every sprite key the reference sidebar needs in
assets/js/runtime/svg-icon.js, and main.min.js injects the <symbol id="icon-*">
set on every frontend page, so no new icon system was needed. The two grids now
use the reference theme's icon-but-box / user-icon-but-box shell (four per row,
em16 icon, 12px muted label) in place of AKSRT's tinted 38px pill, and every
remaining sidebar glyph and arrow resolves through aksrt_icon_markup():

  我的服务  我的等级 trend-color, 官方认证 user-auth, 我的订单 order-color
  功能设置  消息通知 msg-color, 个人资料 user-color, 账户安全 security-color
  资产卡    余额 money-color-2, 积分 points-color
  中心卡    创作收益 merchant-color, 推广收益 money-color
  其它      VIP 入口 vip_1, 抽屉触发器 menu, 箭头统一 right

Dead code went with the swap: the whole .uc-service-grid block including the
unused --cart and --revenue tones, the count badge (no caller ever set count),
and the tone key. The two card selectors that targeted <i> now also cover <svg>
so the icon sizes survive the element change, and the VIP arrow keeps
uc-sidebar-vip__arrow for its hover animation. level/profile/settings gained
their missing tab keys, which completes the icon-but-* class names and lets the
existing .is-active sync cover all six entries.

Verification: node --test across widget-system, navigation, admin,
asset-ledger, dev, front-submit and fixtures (620 tests), plus php -l on the
five changed PHP files. Contract-locked in
tests/widget-system/user-center-sidebar-icons-contract.test.cjs.

inc/helpers/user-center-renderers/sidebar-vip.php

@@ -49,7 +49,8 @@ $sidebar_level = $vip_level > 0 ? $vip_level : $expired_level;
 $sidebar_icon_url = esc_url((string) ($vip_levels[$sidebar_level]['img_icon'] ?? ''));
 $sidebar_icon = $sidebar_icon_url !== ''
 	? '<img' . aksrt_get_lazy_attr('lazy_other', $sidebar_icon_url, 'aksrt-vip-level-icon') . ' alt="" decoding="async">'
-	: '<i class="fa fas fa-certificate" aria-hidden="true"></i>';
+	: aksrt_icon_markup('zibsvg-vip_1');
+$sidebar_arrow = aksrt_icon_markup('zibsvg-right', 'uc-sidebar-vip__arrow');
 ?>
 <a class="uc-sidebar-vip" href="<?php echo esc_url($vip_url); ?>" data-tab="vip">
 	<span class="uc-sidebar-vip__icon"><?php echo $sidebar_icon; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped ?></span>
@@ -57,5 +58,5 @@ $sidebar_icon = $sidebar_icon_url !== ''
 		<strong><?php echo esc_html($title); ?></strong>
 		<small><?php echo esc_html($status); ?></small>
 	</span>
-	<i class="fa fas fa-angle-right uc-sidebar-vip__arrow" aria-hidden="true"></i>
+	<?php echo $sidebar_arrow; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped ?>
 </a>