feat(payment): 优化套餐配置和支付服务

- 简化套餐配置结构，删除冗余的 default.yaml 和 us.yaml
- 优化 Apple IAP 服务和验证逻辑
- 更新套餐数据模型和协议文档
- 添加支付相关测试用例

apps/test/features/payments/data/models/apple_purchase_models_test.dart

@@ -5,16 +5,16 @@ void main() {
   group('VerifyTransactionRequest', () {
     test('toJson includes all required fields', () {
       const request = VerifyTransactionRequest(
-        productCode: 'basic_pack',
-        appStoreProductId: 'com.meeyao.qianwen.basic_pack',
+        productCode: 'starter_pack',
+        appStoreProductId: 'com.meeyao.qianwen.starter_pack',
         transactionId: '1000000123456789',
         signedTransactionInfo: 'eyJhbGciOiJFUzI1NiIs...',
       );
 
       final json = request.toJson();
 
-      expect(json['productCode'], 'basic_pack');
-      expect(json['appStoreProductId'], 'com.meeyao.qianwen.basic_pack');
+      expect(json['productCode'], 'starter_pack');
+      expect(json['appStoreProductId'], 'com.meeyao.qianwen.starter_pack');
       expect(json['transactionId'], '1000000123456789');
       expect(json['signedTransactionInfo'], 'eyJhbGciOiJFUzI1NiIs...');
       expect(json.containsKey('appAccountToken'), false);
@@ -22,8 +22,8 @@ void main() {
 
     test('toJson includes appAccountToken when provided', () {
       const request = VerifyTransactionRequest(
-        productCode: 'basic_pack',
-        appStoreProductId: 'com.meeyao.qianwen.basic_pack',
+        productCode: 'starter_pack',
+        appStoreProductId: 'com.meeyao.qianwen.starter_pack',
         transactionId: '1000000123456789',
         signedTransactionInfo: 'eyJhbGciOiJFUzI1NiIs...',
         appAccountToken: 'abc123def456',
@@ -39,7 +39,7 @@ void main() {
     test('parses granted status correctly', () {
       final json = {
         'status': 'granted',
-        'productCode': 'basic_pack',
+        'productCode': 'starter_pack',
         'transactionId': '1000000123456789',
         'creditsAdded': 100,
         'newBalance': 180,
@@ -49,7 +49,7 @@ void main() {
       final response = VerifyTransactionResponse.fromJson(json);
 
       expect(response.status, VerifyTransactionStatus.granted);
-      expect(response.productCode, 'basic_pack');
+      expect(response.productCode, 'starter_pack');
       expect(response.transactionId, '1000000123456789');
       expect(response.creditsAdded, 100);
       expect(response.newBalance, 180);
@@ -59,7 +59,7 @@ void main() {
     test('parses already_granted status correctly', () {
       final json = {
         'status': 'already_granted',
-        'productCode': 'basic_pack',
+        'productCode': 'starter_pack',
         'transactionId': '1000000123456789',
         'creditsAdded': 0,
         'newBalance': 180,