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/connect_page.dart

@@ -10,13 +10,10 @@ import '../pangolin_theme.dart';
 import '../state/app_providers.dart';
 import '../state/connection_provider.dart';
 import '../state/nodes_provider.dart';
-import '../state/quota_provider.dart';
-import '../widgets/ad_reward_dialog.dart';
 import '../widgets/app_top_bar.dart';
 import '../widgets/connect_button.dart';
 import '../widgets/country_code.dart';
 import '../widgets/pangolin_icons.dart';
-import '../widgets/quota_card.dart';
 
 class ConnectPage extends ConsumerWidget {
   const ConnectPage({super.key, required this.isWide, required this.onOpenNodes});
@@ -31,8 +28,6 @@ class ConnectPage extends ConsumerWidget {
     final conn = ref.watch(connectionProvider);
     final node = ref.watch(effectiveNodeProvider);
     final smart = ref.watch(isSmartSelectProvider);
-    final isFree = ref.watch(isFreePlanProvider);
-    final quota = ref.watch(quotaProvider);
     final stats = ref.watch(vpnStatsProvider).valueOrNull;
     // 账户首拉中 → 整页转圈,先拉到 me(决定免费/会员)再渲染,
     // 避免「先闪免费广告、me 到了再跳会员」。me 是常驻 Notifier,只首启时转一下。
@@ -53,18 +48,11 @@ class ConnectPage extends ConsumerWidget {
       VpnPhase.on => t.capOn,
     };
 
-    // 免费额度耗尽:off 态连接键灰化不可点,点击弹加时(移动看广告 / 桌面升级)。
-    final isDesktop = context.formFactor == FormFactor.desktop;
-    final connectEnabled = !(isFree && quota.isExhausted && conn.phase == VpnPhase.off);
-    void onQuotaBlockedTap() => showQuotaAdFlow(context, ref, isDesktop: isDesktop);
-
     final button = ConnectButton(
       phase: conn.phase,
       elapsed: conn.elapsed,
       offLabel: t.connectNow,
       secureLabel: t.secure,
-      enabled: connectEnabled,
-      onDisabledTap: onQuotaBlockedTap,
       onTap: () => ref.read(connectionProvider.notifier).toggle(),
     );
 
@@ -82,14 +70,6 @@ class ConnectPage extends ConsumerWidget {
     ]);
 
     final infoChildren = <Widget>[
-      if (isFree)
-        QuotaCard(
-          quota: quota,
-          t: t,
-          countdown: conn.freeCountdown,
-          isDesktop: isDesktop,
-          onWatchAd: onQuotaBlockedTap,
-        ),
       if (conn.phase == VpnPhase.on) _SpeedRow(t: t, down: down, up: up, latency: latencyValue),
       _CurrentNodeCard(t: t, node: node, smart: smart, pingLabel: pingLabel, showLabel: isWide, onTap: onOpenNodes),
     ];
@@ -114,8 +94,6 @@ class ConnectPage extends ConsumerWidget {
               offLabel: t.connectNow,
               secureLabel: t.secure,
               size: 176,
-              enabled: connectEnabled,
-              onDisabledTap: onQuotaBlockedTap,
               onTap: () => ref.read(connectionProvider.notifier).toggle(),
             ),
             const SizedBox(height: 24),
@@ -132,19 +110,6 @@ class ConnectPage extends ConsumerWidget {
               ),
             ],
             _NodePill(t: t, node: node, smart: smart, pingLabel: pingLabel),
-            if (isFree) ...[
-              const SizedBox(height: 24),
-              SizedBox(
-                width: 340,
-                child: QuotaCard(
-                  quota: quota,
-                  t: t,
-                  countdown: conn.freeCountdown,
-                  isDesktop: isDesktop,
-                  onWatchAd: onQuotaBlockedTap,
-                ),
-              ),
-            ],
             if (conn.phase == VpnPhase.on) ...[
               const SizedBox(height: 16),
               _SpeedRow(t: t, down: down, up: up, latency: latencyValue),