feat(client): pay v2 支付渠道 switch + 订单列表/详情端到端

购买/支付(Phase B):
- 新 SegSwitch 段控 widget(镜像 .segswitch 原子)
- 购买页重构:顶部支付渠道 switch(默认 USDT→加密货币 / 人民币→支付宝),套餐价随渠道分币种显示,删底部弹窗选方式;点购买直达支付页
- 支付页加订单信息卡(套餐/渠道/金额按币种)
- models:PayChannel + PayCatalogItem.priceUsdtMicro/priceLabel(ch)/perMonthLabel(ch)

订单(P0,全新):
- payment_api.listOrders() + orders_provider(列表 + 详情 family)
- OrdersScreen 列表→详情(状态 pill / 可复制订单号 / 继续支付·重新购买)
- 导航:NavView.orders + desktop_shell 分支 + account 入口

配套:
- l10n +19 getter(支付渠道 4 + 订单 15)×6 语言,l10n 闸绿
- 图标单源迁移 lucide_icons_flutter + pangolin_icons.dart(codegen)
- 联系渠道订正(Telegram/邮件 support@yanmeiai.com/官网) + 前端去广告&时长
- 测试:购买 switch 分币种 + 订单列表/空态/详情 + 假 API listOrders;golden 重录
- flutter analyze 0 error,flutter test 226 全绿

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013nMthbVEmQquxBRKb9Fj8u

client/lib/screens/payment_page.dart

@@ -9,6 +9,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:url_launcher/url_launcher.dart';
 
 import '../l10n/app_text.dart';
+import '../models/payment.dart';
 import '../pangolin_theme.dart';
 import '../state/payment_provider.dart';
 import '../widgets/pangolin_button.dart';
@@ -132,6 +133,48 @@ class _PaymentScreenState extends ConsumerState<PaymentScreen> {
     );
   }
 
+  String _planName(String sku) => switch (sku) {
+        'pro_month' => t.proMonthly,
+        'pro_quarter' => t.proQuarterly,
+        'pro_year' => t.proYearly,
+        _ => sku,
+      };
+
+  // 订单信息卡:套餐名 + 支付渠道 + 金额(金额按所选渠道币种显价)。
+  Widget _orderCard(BuildContext context, PaymentFlowState s) {
+    final c = context.pangolin;
+    final ch = s.method == 'crypto' ? PayChannel.usdt : PayChannel.cny;
+    final chanLabel = ch == PayChannel.usdt ? t.payChannelUsdt : t.payChannelCny;
+    final item = s.item;
+    return _card(c, child: Column(crossAxisAlignment: CrossAxisAlignment.start, children: [
+      Text(t.orderDetailTitle.toUpperCase(),
+          style: PangolinText.caption
+              .copyWith(color: c.fg3, fontWeight: FontWeight.w700, letterSpacing: 0.6)),
+      const SizedBox(height: 10),
+      if (item != null) _orderRow(c, t.orderPlanLabel, _planName(item.sku)),
+      _orderRow(c, t.payChannel, chanLabel),
+      if (item != null) _orderRow(c, t.orderAmountLabel, item.priceLabel(ch), amount: true),
+    ]));
+  }
+
+  Widget _orderRow(PangolinScheme c, String k, String v, {bool amount = false}) => Padding(
+        padding: const EdgeInsets.symmetric(vertical: 4),
+        child: Row(
+          mainAxisAlignment: MainAxisAlignment.spaceBetween,
+          crossAxisAlignment: CrossAxisAlignment.baseline,
+          textBaseline: TextBaseline.alphabetic,
+          children: [
+            Text(k, style: PangolinText.sm.copyWith(color: c.fg3)),
+            Flexible(
+              child: Text(v,
+                  textAlign: TextAlign.right,
+                  style: (amount ? PangolinText.mono : PangolinText.sm).copyWith(
+                      color: amount ? c.accent : c.fg1, fontWeight: FontWeight.w700)),
+            ),
+          ],
+        ),
+      );
+
   Widget _awaiting(BuildContext context, WidgetRef ref, PaymentFlowState s) {
     final c = context.pangolin;
     final session = s.order!.session;
@@ -171,6 +214,8 @@ class _PaymentScreenState extends ConsumerState<PaymentScreen> {
     }
 
     return ListView(padding: const EdgeInsets.fromLTRB(20, 14, 20, 24), children: [
+      _orderCard(context, s),
+      const SizedBox(height: 14),
       renderBody,
       const SizedBox(height: 16),
       Row(children: [