refactor(client): 删除死代码 PlansScreen + NavView.plans + choosePlan l10n(Renew→Purchase 直达后无调用者)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

client/lib/shell/desktop_shell.dart

@@ -49,7 +49,6 @@ class DesktopShell extends ConsumerWidget {
       NavView.account: t.tabMe,
       NavView.contact: t.contactTitle,
       NavView.settings: t.settingsTitle,
-      NavView.plans: t.choosePlan,
       NavView.redeem: t.redeemTitle,
       NavView.devices: t.myDevices,
       NavView.purchase: t.purchaseTitle,
@@ -76,9 +75,6 @@ class DesktopShell extends ConsumerWidget {
         case NavView.settings:
           return const SettingsPage();
         // 账户下钻子页（内容区，顶栏带返回）
-        case NavView.plans:
-          // 只有 pro 走 pay v2 购买通道;team 等仍走既有兑换/联系人工流程。
-          return PlansScreen(t: t, embedded: true, onChoose: (code) => go(code == 'pro' ? NavView.purchase : NavView.redeem));
         case NavView.redeem:
           return RedeemScreen(t: t, embedded: true);
         case NavView.devices: