Fix SilverPay payment integration JSON serialization

- Changed JSON naming policy from CamelCase to SnakeCaseLower for SilverPay API compatibility
- Fixed field name from 'fiat_amount' to 'amount' in request body
- Used unique payment ID instead of order ID to avoid duplicate external_id conflicts
- Modified SilverPayApiResponse to handle string amounts from API
- Added [JsonIgnore] attributes to computed properties to prevent JSON serialization conflicts
- Fixed test compilation errors (mock service and enum casting issues)
- Updated SilverPay endpoint to http://10.0.0.52:8001/

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

LittleShop/Services/CryptoPaymentService.cs

@@ -57,8 +57,11 @@ public class CryptoPaymentService : ICryptoPaymentService
             // Use SilverPAY
             _logger.LogInformation("Creating SilverPAY order for {Currency}", currency);
 
+            // Generate payment ID first to use as external_id
+            var paymentId = Guid.NewGuid();
+
             var silverPayOrder = await _silverPayService.CreateOrderAsync(
-                order.Id.ToString(),
+                paymentId.ToString(),  // Use unique payment ID instead of order ID
                 order.TotalAmount,
                 currency,
                 $"Order #{order.Id} - {order.Items.Count} items",
@@ -67,7 +70,7 @@ public class CryptoPaymentService : ICryptoPaymentService
 
             var cryptoPayment = new CryptoPayment
             {
-                Id = Guid.NewGuid(),
+                Id = paymentId,  // Use the same payment ID
                 OrderId = orderId,
                 Currency = currency,
                 WalletAddress = silverPayOrder.PaymentAddress,

LittleShop/Services/SilverPayService.cs

@@ -54,7 +54,7 @@ public class SilverPayService : ISilverPayService
             var request = new
             {
                 external_id = externalId,
-                fiat_amount = amount,  // Amount in GBP
+                amount = amount,  // Amount in GBP
                 fiat_currency = "GBP",
                 currency = currencyCode,
                 webhook_url = webhookUrl ?? _configuration["SilverPay:DefaultWebhookUrl"],
@@ -63,14 +63,15 @@ public class SilverPayService : ISilverPayService
 
             var json = JsonSerializer.Serialize(request, new JsonSerializerOptions
             {
-                PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+                PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
                 DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull
             });
 
             var content = new StringContent(json, Encoding.UTF8, "application/json");
 
-            _logger.LogDebug("Creating SilverPAY order - External ID: {ExternalId}, Amount: {Amount} GBP, Currency: {Currency}",
+            _logger.LogInformation("Creating SilverPAY order - External ID: {ExternalId}, Amount: {Amount} GBP, Currency: {Currency}",
                 externalId, amount, currencyCode);
+            _logger.LogInformation("SilverPAY request body: {RequestBody}", json);
 
             // Add timeout to prevent hanging
             using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(10));
@@ -260,7 +261,10 @@ public class SilverPayService : ISilverPayService
         public string ExternalId { get; set; } = string.Empty;
 
         [JsonPropertyName("amount")]
-        public decimal Amount { get; set; }
+        public string AmountString { get; set; } = string.Empty;
+
+        [JsonIgnore]
+        public decimal Amount => decimal.TryParse(AmountString, out var amount) ? amount : 0;
 
         [JsonPropertyName("currency")]
         public string Currency { get; set; } = string.Empty;
@@ -284,7 +288,10 @@ public class SilverPayService : ISilverPayService
         public Dictionary<string, object>? PaymentDetails { get; set; }
 
         [JsonPropertyName("crypto_amount")]
-        public decimal? CryptoAmount { get; set; }
+        public string? CryptoAmountString { get; set; }
+
+        [JsonIgnore]
+        public decimal? CryptoAmount => decimal.TryParse(CryptoAmountString, out var amount) ? amount : null;
 
         [JsonPropertyName("tx_hash")]
         public string? TransactionHash { get; set; }