feat: 实现 iOS Apple Pay 内购支付功能

前端:
- 集成 in_app_purchase 插件，实现 IAP 支付流程
- 添加支付模块 (payments/) 处理产品获取、购买、验证
- 积分中心页面集成 Apple Pay 购买入口
- 设置页面重构: 关于/隐私/协议直接展示，删除 legal_center 子页面
- 修复欢迎引导页滚动检测阈值问题
- 修复解卦结果页 iOS 侧滑返回手势被阻止的问题
- 邀请码绑定按钮临时禁用（待后端实现）

后端:
- 新增 apple_iap_transactions 表记录交易
- 实现 Apple 服务器端验证 (App Store Server API)
- 支付成功后自动发放积分
- 支持 Sandbox/Production 环境切换
- 添加退款处理和交易状态机

协议:
- 更新积分流水协议，支持 purchase/refund 类型
- 新增 PAYMENT_* 错误码

apps/lib/l10n/app_en.arb

@@ -505,5 +505,11 @@
   "feedbackContentRequired": "Please enter feedback content",
   "feedbackContentTooLong": "Feedback content cannot exceed 500 characters",
   "feedbackTooManyImages": "Maximum 3 images allowed",
-  "feedbackImageTooLarge": "Image size cannot exceed 5MB"
+  "feedbackImageTooLarge": "Image size cannot exceed 5MB",
+  "paymentSuccess": "Purchase successful",
+  "paymentVerifyFailed": "Purchase verification failed, please try again later",
+  "paymentProductNotFound": "Product temporarily unavailable",
+  "paymentStarterPackIneligible": "Starter pack is limited to one purchase per user",
+  "paymentProductUnavailable": "Product temporarily unavailable",
+  "paymentPending": "Apple is processing, please wait"
 }

apps/lib/l10n/app_localizations.dart

@@ -2432,6 +2432,42 @@ abstract class AppLocalizations {
   /// In zh, this message translates to:
   /// **'图片大小不能超过5MB'**
   String get feedbackImageTooLarge;
+
+  /// No description provided for @paymentSuccess.
+  ///
+  /// In zh, this message translates to:
+  /// **'购买成功'**
+  String get paymentSuccess;
+
+  /// No description provided for @paymentVerifyFailed.
+  ///
+  /// In zh, this message translates to:
+  /// **'购买验证失败，请稍后重试'**
+  String get paymentVerifyFailed;
+
+  /// No description provided for @paymentProductNotFound.
+  ///
+  /// In zh, this message translates to:
+  /// **'商品暂时不可用'**
+  String get paymentProductNotFound;
+
+  /// No description provided for @paymentStarterPackIneligible.
+  ///
+  /// In zh, this message translates to:
+  /// **'新手包每位用户仅限购买一次'**
+  String get paymentStarterPackIneligible;
+
+  /// No description provided for @paymentProductUnavailable.
+  ///
+  /// In zh, this message translates to:
+  /// **'商品暂时不可用'**
+  String get paymentProductUnavailable;
+
+  /// No description provided for @paymentPending.
+  ///
+  /// In zh, this message translates to:
+  /// **'Apple 正在处理中，请稍候'**
+  String get paymentPending;
 }
 
 class _AppLocalizationsDelegate

apps/lib/l10n/app_localizations_en.dart

@@ -1282,4 +1282,24 @@ class AppLocalizationsEn extends AppLocalizations {
 
   @override
   String get feedbackImageTooLarge => 'Image size cannot exceed 5MB';
+
+  @override
+  String get paymentSuccess => 'Purchase successful';
+
+  @override
+  String get paymentVerifyFailed =>
+      'Purchase verification failed, please try again later';
+
+  @override
+  String get paymentProductNotFound => 'Product temporarily unavailable';
+
+  @override
+  String get paymentStarterPackIneligible =>
+      'Starter pack is limited to one purchase per user';
+
+  @override
+  String get paymentProductUnavailable => 'Product temporarily unavailable';
+
+  @override
+  String get paymentPending => 'Apple is processing, please wait';
 }

apps/lib/l10n/app_localizations_zh.dart

@@ -1225,6 +1225,24 @@ class AppLocalizationsZh extends AppLocalizations {
 
   @override
   String get feedbackImageTooLarge => '图片大小不能超过5MB';
+
+  @override
+  String get paymentSuccess => '购买成功';
+
+  @override
+  String get paymentVerifyFailed => '购买验证失败，请稍后重试';
+
+  @override
+  String get paymentProductNotFound => '商品暂时不可用';
+
+  @override
+  String get paymentStarterPackIneligible => '新手包每位用户仅限购买一次';
+
+  @override
+  String get paymentProductUnavailable => '商品暂时不可用';
+
+  @override
+  String get paymentPending => 'Apple 正在处理中，请稍候';
 }
 
 /// The translations for Chinese, using the Han script (`zh_Hant`).
@@ -2204,4 +2222,22 @@ class AppLocalizationsZhHant extends AppLocalizationsZh {
 
   @override
   String get feedbackImageTooLarge => '圖片大小不能超過5MB';
+
+  @override
+  String get paymentSuccess => '購買成功';
+
+  @override
+  String get paymentVerifyFailed => '購買驗證失敗，請稍後重試';
+
+  @override
+  String get paymentProductNotFound => '商品暫時不可用';
+
+  @override
+  String get paymentStarterPackIneligible => '新手包每位用戶僅限購買一次';
+
+  @override
+  String get paymentProductUnavailable => '商品暫時不可用';
+
+  @override
+  String get paymentPending => 'Apple 正在處理中，請稍候';
 }

apps/lib/l10n/app_zh.arb

@@ -505,5 +505,11 @@
   "feedbackContentRequired": "请输入反馈内容",
   "feedbackContentTooLong": "反馈内容不能超过500字",
   "feedbackTooManyImages": "最多只能上传3张图片",
-  "feedbackImageTooLarge": "图片大小不能超过5MB"
+  "feedbackImageTooLarge": "图片大小不能超过5MB",
+  "paymentSuccess": "购买成功",
+  "paymentVerifyFailed": "购买验证失败，请稍后重试",
+  "paymentProductNotFound": "商品暂时不可用",
+  "paymentStarterPackIneligible": "新手包每位用户仅限购买一次",
+  "paymentProductUnavailable": "商品暂时不可用",
+  "paymentPending": "Apple 正在处理中，请稍候"
 }

apps/lib/l10n/app_zh_hant.arb

@@ -407,5 +407,11 @@
   "feedbackContentRequired": "請輸入回饋內容",
   "feedbackContentTooLong": "回饋內容不能超過500字",
   "feedbackTooManyImages": "最多只能上傳3張圖片",
-  "feedbackImageTooLarge": "圖片大小不能超過5MB"
+  "feedbackImageTooLarge": "圖片大小不能超過5MB",
+  "paymentSuccess": "購買成功",
+  "paymentVerifyFailed": "購買驗證失敗，請稍後重試",
+  "paymentProductNotFound": "商品暫時不可用",
+  "paymentStarterPackIneligible": "新手包每位用戶僅限購買一次",
+  "paymentProductUnavailable": "商品暫時不可用",
+  "paymentPending": "Apple 正在處理中，請稍候"
 }