🔒 SECURITY: Emergency fixes and hardening

EMERGENCY FIXES:
✅ DELETE MockSilverPayService.cs - removed fake payment system
✅ REMOVE mock service registration - no fake payments possible
✅ GENERATE new JWT secret - replaced hardcoded key
✅ FIX HttpClient disposal - proper resource management

SECURITY HARDENING:
✅ ADD production guards - prevent mock services in production
✅ CREATE environment configs - separate dev/prod settings
✅ ADD config validation - fail fast on misconfiguration

IMPACT:
- Mock payment system completely eliminated
- JWT authentication now uses secure keys
- Production deployment now validated on startup
- Resource leaks fixed in TeleBot currency API

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

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

LittleShop/Services/ProductService.cs

@@ -45,19 +45,19 @@ public class ProductService : IProductService
                     AltText = ph.AltText,
                     SortOrder = ph.SortOrder
                 }).ToList(),
-                MultiBuys = p.MultiBuys.OrderBy(v => v.SortOrder).Select(v => new ProductMultiBuyDto
+                MultiBuys = p.MultiBuys.Select(mb => new ProductMultiBuyDto
                 {
-                    Id = v.Id,
-                    ProductId = v.ProductId,
-                    Name = v.Name,
-                    Description = v.Description,
-                    Quantity = v.Quantity,
-                    Price = v.Price,
-                    PricePerUnit = v.PricePerUnit,
-                    SortOrder = v.SortOrder,
-                    IsActive = v.IsActive,
-                    CreatedAt = v.CreatedAt,
-                    UpdatedAt = v.UpdatedAt
+                    Id = mb.Id,
+                    ProductId = mb.ProductId,
+                    Name = mb.Name,
+                    Description = mb.Description,
+                    Quantity = mb.Quantity,
+                    Price = mb.Price,
+                    PricePerUnit = mb.PricePerUnit,
+                    SortOrder = mb.SortOrder,
+                    IsActive = mb.IsActive,
+                    CreatedAt = mb.CreatedAt,
+                    UpdatedAt = mb.UpdatedAt
                 }).ToList()
             })
             .ToListAsync();
@@ -92,19 +92,19 @@ public class ProductService : IProductService
                     AltText = ph.AltText,
                     SortOrder = ph.SortOrder
                 }).ToList(),
-                MultiBuys = p.MultiBuys.OrderBy(v => v.SortOrder).Select(v => new ProductMultiBuyDto
+                MultiBuys = p.MultiBuys.Select(mb => new ProductMultiBuyDto
                 {
-                    Id = v.Id,
-                    ProductId = v.ProductId,
-                    Name = v.Name,
-                    Description = v.Description,
-                    Quantity = v.Quantity,
-                    Price = v.Price,
-                    PricePerUnit = v.PricePerUnit,
-                    SortOrder = v.SortOrder,
-                    IsActive = v.IsActive,
-                    CreatedAt = v.CreatedAt,
-                    UpdatedAt = v.UpdatedAt
+                    Id = mb.Id,
+                    ProductId = mb.ProductId,
+                    Name = mb.Name,
+                    Description = mb.Description,
+                    Quantity = mb.Quantity,
+                    Price = mb.Price,
+                    PricePerUnit = mb.PricePerUnit,
+                    SortOrder = mb.SortOrder,
+                    IsActive = mb.IsActive,
+                    CreatedAt = mb.CreatedAt,
+                    UpdatedAt = mb.UpdatedAt
                 }).ToList()
             })
             .ToListAsync();