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/Program.cs

@@ -34,7 +34,7 @@ else
 }
 
 // Authentication - Cookie for Admin Panel, JWT for API
-var jwtKey = builder.Configuration["Jwt:Key"] ?? "YourSuperSecretKeyThatIsAtLeast32CharactersLong!";
+var jwtKey = builder.Configuration["Jwt:Key"] ?? "ThisIsASuperSecretKeyForJWTAuthenticationThatIsDefinitelyLongerThan32Characters!";
 var jwtIssuer = builder.Configuration["Jwt:Issuer"] ?? "LittleShop";
 var jwtAudience = builder.Configuration["Jwt:Audience"] ?? "LittleShop";
 
@@ -76,7 +76,8 @@ builder.Services.AddScoped<ICategoryService, CategoryService>();
 builder.Services.AddScoped<IProductService, ProductService>();
 builder.Services.AddScoped<IOrderService, OrderService>();
 builder.Services.AddScoped<ICryptoPaymentService, CryptoPaymentService>();
-builder.Services.AddScoped<IBTCPayServerService, BTCPayServerService>();
+// BTCPay removed - using SilverPAY only
+builder.Services.AddHttpClient<ISilverPayService, SilverPayService>();
 builder.Services.AddScoped<IShippingRateService, ShippingRateService>();
 builder.Services.AddScoped<IRoyalMailService, RoyalMailShippingService>();
 builder.Services.AddHttpClient<IRoyalMailService, RoyalMailShippingService>();