🔒 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/AddMultiBuysTable.csx

@@ -0,0 +1,32 @@
+#r "nuget: Microsoft.Data.Sqlite, 9.0.1"
+
+using Microsoft.Data.Sqlite;
+
+var connectionString = @"Data Source=C:\Production\Source\LittleShop\LittleShop\littleshop.db";
+
+using (var connection = new SqliteConnection(connectionString))
+{
+    connection.Open();
+
+    var sql = @"
+        CREATE TABLE IF NOT EXISTS ProductMultiBuys (
+            Id TEXT PRIMARY KEY NOT NULL,
+            ProductId TEXT NOT NULL,
+            Name TEXT NOT NULL,
+            Description TEXT NOT NULL DEFAULT '',
+            Quantity INTEGER NOT NULL,
+            Price REAL NOT NULL,
+            PricePerUnit REAL NOT NULL,
+            SortOrder INTEGER NOT NULL DEFAULT 0,
+            IsActive INTEGER NOT NULL DEFAULT 1,
+            CreatedAt TEXT NOT NULL,
+            UpdatedAt TEXT NOT NULL,
+            FOREIGN KEY (ProductId) REFERENCES Products(Id) ON DELETE CASCADE
+        )";
+
+    using (var command = new SqliteCommand(sql, connection))
+    {
+        command.ExecuteNonQuery();
+        Console.WriteLine("ProductMultiBuys table created successfully!");
+    }
+}