Remove BTCPay completely, integrate SilverPAY only, configure TeleBot with real token

- Removed all BTCPay references from services and configuration
- Implemented SilverPAY as sole payment provider (no fallback)
- Fixed JWT authentication with proper key length (256+ bits)
- Added UsersController with full CRUD operations
- Updated User model with Email and Role properties
- Configured TeleBot with real Telegram bot token
- Fixed launchSettings.json with JWT environment variable
- E2E tests passing for authentication, catalog, orders
- Payment creation pending SilverPAY server fix

🤖 Generated with Claude Code

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

LittleShop/Services/ISilverPayService.cs

@@ -0,0 +1,83 @@
+using LittleShop.Enums;
+
+namespace LittleShop.Services;
+
+public interface ISilverPayService
+{
+    /// <summary>
+    /// Create a new payment order in SilverPAY
+    /// </summary>
+    /// <param name="externalId">External order ID (LittleShop order ID)</param>
+    /// <param name="amount">Amount in fiat currency (GBP)</param>
+    /// <param name="currency">Cryptocurrency to accept</param>
+    /// <param name="description">Optional order description</param>
+    /// <param name="webhookUrl">Optional webhook URL for payment notifications</param>
+    /// <returns>SilverPAY order details including payment address</returns>
+    Task<SilverPayOrderResponse> CreateOrderAsync(
+        string externalId,
+        decimal amount,
+        CryptoCurrency currency,
+        string? description = null,
+        string? webhookUrl = null);
+
+    /// <summary>
+    /// Get the status of a SilverPAY order
+    /// </summary>
+    /// <param name="orderId">SilverPAY order ID</param>
+    /// <returns>Order status and payment details</returns>
+    Task<SilverPayOrderResponse?> GetOrderStatusAsync(string orderId);
+
+    /// <summary>
+    /// Validate webhook signature from SilverPAY
+    /// </summary>
+    /// <param name="payload">Webhook payload</param>
+    /// <param name="signature">Webhook signature header</param>
+    /// <returns>True if signature is valid</returns>
+    Task<bool> ValidateWebhookAsync(string payload, string signature);
+
+    /// <summary>
+    /// Get current exchange rate for crypto to fiat
+    /// </summary>
+    /// <param name="cryptoCurrency">Cryptocurrency symbol</param>
+    /// <param name="fiatCurrency">Fiat currency (GBP, USD, EUR)</param>
+    /// <returns>Current exchange rate</returns>
+    Task<decimal?> GetExchangeRateAsync(string cryptoCurrency, string fiatCurrency = "GBP");
+}
+
+/// <summary>
+/// Response from SilverPAY order creation/status
+/// </summary>
+public class SilverPayOrderResponse
+{
+    public string Id { get; set; } = string.Empty;
+    public string ExternalId { get; set; } = string.Empty;
+    public decimal Amount { get; set; }
+    public string Currency { get; set; } = string.Empty;
+    public string PaymentAddress { get; set; } = string.Empty;
+    public string Status { get; set; } = string.Empty;
+    public DateTime CreatedAt { get; set; }
+    public DateTime ExpiresAt { get; set; }
+    public DateTime? PaidAt { get; set; }
+    public Dictionary<string, object>? PaymentDetails { get; set; }
+
+    // Additional fields for crypto amounts
+    public decimal? CryptoAmount { get; set; }
+    public string? TransactionHash { get; set; }
+    public int? Confirmations { get; set; }
+}
+
+/// <summary>
+/// Webhook notification from SilverPAY
+/// </summary>
+public class SilverPayWebhookNotification
+{
+    public string OrderId { get; set; } = string.Empty;
+    public string ExternalId { get; set; } = string.Empty;
+    public string Status { get; set; } = string.Empty;
+    public string Address { get; set; } = string.Empty;
+    public string? TxHash { get; set; }
+    public decimal Amount { get; set; }
+    public int Confirmations { get; set; }
+    public int? BlockHeight { get; set; }
+    public DateTime Timestamp { get; set; }
+}