fix(reward): TG webhook 空 secret fail-fast + 首充奖励文案六语 15→7(终审必修)

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

client/lib/l10n/strings_en.dart

@@ -488,7 +488,7 @@ class StringsEn extends AppText {
   @override
   String get inviteRewardRegister => 'Sign up · +3 days each';
   @override
-  String get inviteRewardFirstBuy => 'First purchase · +15 days each';
+  String get inviteRewardFirstBuy => 'First purchase · +7 days each';
   @override
   String get inviteRewardJoinTg => 'Join TG · +3 days';
   @override

client/lib/l10n/strings_es.dart

@@ -489,7 +489,7 @@ class StringsEs extends AppText {
   @override
   String get inviteRewardRegister => 'Registro de amigo · +3 días cada uno';
   @override
-  String get inviteRewardFirstBuy => 'Primera compra del amigo · +15 días cada uno';
+  String get inviteRewardFirstBuy => 'Primera compra del amigo · +7 días cada uno';
   @override
   String get inviteRewardJoinTg => 'Unirse al canal de TG · +3 días';
   @override

client/lib/l10n/strings_ja.dart

@@ -489,7 +489,7 @@ class StringsJa extends AppText {
   @override
   String get inviteRewardRegister => '友達が登録 · 双方に3日間付与';
   @override
-  String get inviteRewardFirstBuy => '友達が初回購入 · 双方に15日間付与';
+  String get inviteRewardFirstBuy => '友達が初回購入 · 双方に7日間付与';
   @override
   String get inviteRewardJoinTg => 'TGチャンネルに参加 · 3日間付与';
   @override

client/lib/l10n/strings_ko.dart

@@ -489,7 +489,7 @@ class StringsKo extends AppText {
   @override
   String get inviteRewardRegister => '친구 가입 · 양쪽 각 3일 지급';
   @override
-  String get inviteRewardFirstBuy => '친구 첫 구매 · 양쪽 각 15일 지급';
+  String get inviteRewardFirstBuy => '친구 첫 구매 · 양쪽 각 7일 지급';
   @override
   String get inviteRewardJoinTg => 'TG 채널 가입 · 3일 지급';
   @override

client/lib/l10n/strings_ru.dart

@@ -489,7 +489,7 @@ class StringsRu extends AppText {
   @override
   String get inviteRewardRegister => 'Регистрация друга · +3 дня каждому';
   @override
-  String get inviteRewardFirstBuy => 'Первая покупка друга · +15 дней каждому';
+  String get inviteRewardFirstBuy => 'Первая покупка друга · +7 дней каждому';
   @override
   String get inviteRewardJoinTg => 'Вступление в TG-канал · +3 дня';
   @override

client/lib/l10n/strings_zh.dart

@@ -482,7 +482,7 @@ class StringsZh extends AppText {
   @override
   String get inviteRewardRegister => '好友注册 · 双方各得 3 天';
   @override
-  String get inviteRewardFirstBuy => '好友首购 · 双方各得 15 天';
+  String get inviteRewardFirstBuy => '好友首购 · 双方各得 7 天';
   @override
   String get inviteRewardJoinTg => '加入 TG 频道 · 得 3 天';
   @override