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/DTOs/UserDto.cs

@@ -4,6 +4,8 @@ public class UserDto
 {
     public Guid Id { get; set; }
     public string Username { get; set; } = string.Empty;
+    public string? Email { get; set; }
+    public string Role { get; set; } = "Staff";
     public DateTime CreatedAt { get; set; }
     public bool IsActive { get; set; }
 }
@@ -12,11 +14,15 @@ public class CreateUserDto
 {
     public string Username { get; set; } = string.Empty;
     public string Password { get; set; } = string.Empty;
+    public string? Email { get; set; }
+    public string? Role { get; set; }
 }
 
 public class UpdateUserDto
 {
     public string? Username { get; set; }
     public string? Password { get; set; }
+    public string? Email { get; set; }
+    public string? Role { get; set; }
     public bool? IsActive { get; set; }
 }