refactor(contact): 渠道抽单源常量 + RedeemScreen 删去哪买引流卡(仅留兑换码)

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

client/lib/screens/contact_page.dart

@@ -8,6 +8,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import '../l10n/app_text.dart';
 import '../pangolin_theme.dart';
 import '../services/channel_launch.dart';
+import '../services/contact_channels.dart';
 import '../state/app_providers.dart';
 import '../widgets/pangolin_icons.dart';
 
@@ -19,11 +20,19 @@ class ContactPage extends ConsumerWidget {
     final c = context.pangolin;
     final t = ref.watch(appTextProvider);
 
-    final channels = <({IconData icon, String name, String sub, bool accent})>[
-      (icon: PangolinIcons.send, name: 'Telegram', sub: '@pangolin_app', accent: true),
-      (icon: PangolinIcons.mail, name: t.contactEmail, sub: 'support@yanmeiai.com', accent: false),
-      (icon: PangolinIcons.globe, name: t.contactWebsite, sub: 'pangolin.yanmeiai.com', accent: false),
-    ];
+    final channels = kContactChannels
+        .map((ch) => (
+              icon: ch.icon,
+              name: switch (ch.nameKey) {
+                'telegram' => 'Telegram',
+                'email' => t.contactEmail,
+                'website' => t.contactWebsite,
+                _ => ch.nameKey,
+              },
+              sub: ch.sub,
+              accent: ch.accent,
+            ))
+        .toList();
 
     return SingleChildScrollView(
       padding: const EdgeInsets.fromLTRB(32, 16, 32, 24),