🔒 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.Client/Services/CatalogService.cs

@@ -116,14 +116,14 @@ public class CatalogService : ICatalogService
         try
         {
             var response = await _httpClient.GetAsync($"api/catalog/products/{id}");
-            
+
             if (response.IsSuccessStatusCode)
             {
                 var product = await response.Content.ReadFromJsonAsync<Product>();
                 if (product != null)
                     return ApiResponse<Product>.Success(product);
             }
-            
+
             var error = await response.Content.ReadAsStringAsync();
             return ApiResponse<Product>.Failure(error, response.StatusCode);
         }
@@ -131,7 +131,31 @@ public class CatalogService : ICatalogService
         {
             _logger.LogError(ex, "Failed to get product {ProductId}", id);
             return ApiResponse<Product>.Failure(
-                ex.Message, 
+                ex.Message,
+                System.Net.HttpStatusCode.InternalServerError);
+        }
+    }
+
+    public async Task<ApiResponse<List<string>>> GetAvailableCurrenciesAsync()
+    {
+        try
+        {
+            var response = await _httpClient.GetAsync("api/currency/available");
+
+            if (response.IsSuccessStatusCode)
+            {
+                var currencies = await response.Content.ReadFromJsonAsync<List<string>>();
+                return ApiResponse<List<string>>.Success(currencies ?? new List<string>());
+            }
+
+            var error = await response.Content.ReadAsStringAsync();
+            return ApiResponse<List<string>>.Failure(error, response.StatusCode);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to get available currencies");
+            return ApiResponse<List<string>>.Failure(
+                ex.Message,
                 System.Net.HttpStatusCode.InternalServerError);
         }
     }