feat(client/purchase): 全员优惠月付特殊卡片(¥6/$1,随渠道显价)

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

client/lib/l10n/app_text.dart

@@ -587,6 +587,8 @@ abstract class AppText {
   String get orderRebuy;
   String get payMethodNezha;       // 请复制内容后在支付宝内打开 / Copy and open in Alipay
   String get orderStatusExpired;     // 已过期 / Expired
+  String get promoBadge;             // 超值月付 / Best value
+  String get promoOriginalPrice;     // 原价 / Was
 
   // ── 邀请好友(Spec ②占位) ──
   String get inviteEntry;          // 邀请好友得会员 / Invite friends, earn membership

client/lib/l10n/strings_en.dart

@@ -511,4 +511,8 @@ class StringsEn extends AppText {
   String get settingsGroupAbout => 'About';
   @override
   String get orderStatusExpired => 'Expired';
+  @override
+  String get promoBadge => 'Limited-time offer';
+  @override
+  String get promoOriginalPrice => 'Was';
 }

client/lib/l10n/strings_es.dart

@@ -512,4 +512,8 @@ class StringsEs extends AppText {
   String get settingsGroupAbout => 'Acerca de';
   @override
   String get orderStatusExpired => 'Caducado';
+  @override
+  String get promoBadge => 'Oferta especial';
+  @override
+  String get promoOriginalPrice => 'Antes';
 }

client/lib/l10n/strings_ja.dart

@@ -512,4 +512,8 @@ class StringsJa extends AppText {
   String get settingsGroupAbout => 'このアプリについて';
   @override
   String get orderStatusExpired => '期限切れ';
+  @override
+  String get promoBadge => '期間限定オファー';
+  @override
+  String get promoOriginalPrice => '通常価格';
 }

client/lib/l10n/strings_ko.dart

@@ -512,4 +512,8 @@ class StringsKo extends AppText {
   String get settingsGroupAbout => '정보';
   @override
   String get orderStatusExpired => '만료됨';
+  @override
+  String get promoBadge => '한정 특가';
+  @override
+  String get promoOriginalPrice => '정가';
 }

client/lib/l10n/strings_ru.dart

@@ -512,4 +512,8 @@ class StringsRu extends AppText {
   String get settingsGroupAbout => 'О приложении';
   @override
   String get orderStatusExpired => 'Истёк';
+  @override
+  String get promoBadge => 'Спецпредложение';
+  @override
+  String get promoOriginalPrice => 'Было';
 }

client/lib/l10n/strings_zh.dart

@@ -505,4 +505,8 @@ class StringsZh extends AppText {
   String get settingsGroupAbout => '关于';
   @override
   String get orderStatusExpired => '已过期';
+  @override
+  String get promoBadge => '限时优惠';
+  @override
+  String get promoOriginalPrice => '原价';
 }