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/l10n/strings_en.dart

@@ -1,6 +1,6 @@
 // strings_en.dart — English copy resources (single-language display)
 //
-// Red-line words forbidden: VPN / 翻墙 / 科学上网 / 突破封锁 / 自由穿越 / Go anywhere.
+// Red-line words forbidden — see design/CLAUDE.md §1 rule 13 (no censorship-circumvention terms).
 // Positioning: network acceleration / experience optimization + privacy.
 // Plan numbers follow design/CLAUDE.md §7.
 import 'app_text.dart';
@@ -65,7 +65,7 @@ class StringsEn extends AppText {
   @override
   String get watchAdMore => 'Watch ad for more time';
   @override
-  String get quotaExhaustedNotice => 'Daily free time used up. Watch an ad to add time or upgrade.';
+  String get quotaExhaustedNotice => "You've used today's free time. Upgrade to keep connecting.";
   @override
   String get adPlaying => 'Ad playing…';
   @override
@@ -311,6 +311,8 @@ class StringsEn extends AppText {
   @override
   String get contactStore => 'Self-serve store';
   @override
+  String get contactWebsite => 'Website';
+  @override
   String get contactHoursTitle => 'Support hours';
   @override
   String get contactHours => 'Daily 9:00 – 24:00 (GMT+8)';
@@ -427,4 +429,44 @@ class StringsEn extends AppText {
   String get cancelOrder => 'Cancel order';
   @override
   String get qrNotSupported => 'Copy and open in Alipay';
+
+  // ── 支付渠道 switch + 订单 ──
+  @override
+  String get payChannel => 'Payment channel';
+  @override
+  String get payChannelUsdt => 'USDT · Crypto';
+  @override
+  String get payChannelCny => 'CNY · Alipay';
+  @override
+  String get perMonthSuffix => ' /mo';
+  @override
+  String get ordersTitle => 'My orders';
+  @override
+  String get orderDetailTitle => 'Order details';
+  @override
+  String get ordersEmpty => 'No orders yet';
+  @override
+  String get orderNoLabel => 'Order no.';
+  @override
+  String get orderPlanLabel => 'Plan';
+  @override
+  String get orderMethodLabel => 'Payment method';
+  @override
+  String get orderAmountLabel => 'Amount';
+  @override
+  String get orderCreatedLabel => 'Created';
+  @override
+  String get orderPaidLabel => 'Paid at';
+  @override
+  String get orderStatusPaid => 'Activated';
+  @override
+  String get orderStatusCanceled => 'Canceled';
+  @override
+  String get orderContinuePay => 'Continue payment';
+  @override
+  String get orderRefresh => 'Refresh';
+  @override
+  String get orderRebuy => 'Buy again';
+  @override
+  String get payMethodNezha => 'Nazhapay';
 }