Implement product multi-buys and variants system

Major restructuring of product variations:
- Renamed ProductVariation to ProductMultiBuy for quantity-based pricing (e.g., "3 for £25")
- Added new ProductVariant model for string-based options (colors, flavors)
- Complete separation of multi-buy pricing from variant selection

Features implemented:
- Multi-buy deals with automatic price-per-unit calculation
- Product variants for colors/flavors/sizes with stock tracking
- TeleBot checkout supports both multi-buys and variant selection
- Shopping cart correctly calculates multi-buy bundle prices
- Order system tracks selected variants and multi-buy choices
- Real-time bot activity monitoring with SignalR
- Public bot directory page with QR codes for Telegram launch
- Admin dashboard shows multi-buy and variant metrics

Technical changes:
- Updated all DTOs, services, and controllers
- Fixed cart total calculation for multi-buy bundles
- Comprehensive test coverage for new functionality
- All existing tests passing with new features

Database changes:
- Migrated ProductVariations to ProductMultiBuys
- Added ProductVariants table
- Updated OrderItems to track variants

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

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

LittleShop/Controllers/BotDirectoryController.cs

@@ -0,0 +1,152 @@
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+using QRCoder;
+using LittleShop.Data;
+using LittleShop.DTOs;
+using LittleShop.Enums;
+
+namespace LittleShop.Controllers;
+
+public class BotDirectoryController : Controller
+{
+    private readonly LittleShopContext _context;
+    private readonly ILogger<BotDirectoryController> _logger;
+
+    public BotDirectoryController(LittleShopContext context, ILogger<BotDirectoryController> logger)
+    {
+        _context = context;
+        _logger = logger;
+    }
+
+    // GET: /bots
+    [HttpGet("/bots")]
+    public async Task<IActionResult> Index()
+    {
+        var bots = await _context.Bots
+            .Where(b => b.Status == BotStatus.Active && b.IsActive)
+            .OrderBy(b => b.Name)
+            .Select(b => new BotDirectoryDto
+            {
+                Id = b.Id,
+                Name = b.Name,
+                Description = b.Description,
+                Type = b.Type.ToString(),
+                PersonalityName = b.PersonalityName,
+                TelegramUsername = b.Settings.Contains("\"telegram_username\":")
+                    ? ExtractTelegramUsername(b.Settings)
+                    : b.PlatformUsername,
+                LastSeenAt = b.LastSeenAt,
+                CreatedAt = b.CreatedAt
+            })
+            .ToListAsync();
+
+        return View(bots);
+    }
+
+    // GET: /bots/qr/{id}
+    [HttpGet("/bots/qr/{id}")]
+    public async Task<IActionResult> GetQRCode(Guid id)
+    {
+        var bot = await _context.Bots
+            .Where(b => b.Id == id && b.Status == BotStatus.Active)
+            .FirstOrDefaultAsync();
+
+        if (bot == null)
+        {
+            return NotFound();
+        }
+
+        // Extract Telegram username from settings JSON or use platform username
+        string? telegramUsername = ExtractTelegramUsername(bot.Settings) ?? bot.PlatformUsername;
+
+        if (string.IsNullOrEmpty(telegramUsername))
+        {
+            return NotFound("Bot does not have a Telegram username configured");
+        }
+
+        // Generate Telegram deep link
+        string telegramUrl = $"https://t.me/{telegramUsername}";
+
+        // Generate QR code
+        using (QRCodeGenerator qrGenerator = new QRCodeGenerator())
+        {
+            QRCodeData qrCodeData = qrGenerator.CreateQrCode(telegramUrl, QRCodeGenerator.ECCLevel.Q);
+            using (PngByteQRCode qrCode = new PngByteQRCode(qrCodeData))
+            {
+                byte[] qrCodeImage = qrCode.GetGraphic(20);
+                return File(qrCodeImage, "image/png");
+            }
+        }
+    }
+
+    private static string? ExtractTelegramUsername(string settings)
+    {
+        try
+        {
+            var json = System.Text.Json.JsonDocument.Parse(settings);
+            if (json.RootElement.TryGetProperty("telegram_username", out var username))
+            {
+                return username.GetString();
+            }
+        }
+        catch
+        {
+            // JSON parsing failed
+        }
+        return null;
+    }
+}
+
+public class BotDirectoryDto
+{
+    public Guid Id { get; set; }
+    public string Name { get; set; } = string.Empty;
+    public string Description { get; set; } = string.Empty;
+    public string Type { get; set; } = string.Empty;
+    public string PersonalityName { get; set; } = string.Empty;
+    public string? TelegramUsername { get; set; }
+    public DateTime? LastSeenAt { get; set; }
+    public DateTime CreatedAt { get; set; }
+
+    public string GetBadgeColor()
+    {
+        return Type.ToLower() switch
+        {
+            "sales" => "primary",
+            "support" => "success",
+            "marketing" => "warning",
+            "technical" => "info",
+            _ => "secondary"
+        };
+    }
+
+    public string GetStatusBadge()
+    {
+        if (!LastSeenAt.HasValue)
+            return "Never Connected";
+
+        var timeSinceLastSeen = DateTime.UtcNow - LastSeenAt.Value;
+        if (timeSinceLastSeen.TotalMinutes < 5)
+            return "Online";
+        else if (timeSinceLastSeen.TotalHours < 1)
+            return "Recently Active";
+        else if (timeSinceLastSeen.TotalDays < 1)
+            return "Active Today";
+        else
+            return $"Last seen {timeSinceLastSeen.Days} days ago";
+    }
+
+    public string GetStatusColor()
+    {
+        if (!LastSeenAt.HasValue)
+            return "secondary";
+
+        var timeSinceLastSeen = DateTime.UtcNow - LastSeenAt.Value;
+        if (timeSinceLastSeen.TotalMinutes < 5)
+            return "success";
+        else if (timeSinceLastSeen.TotalHours < 1)
+            return "info";
+        else
+            return "secondary";
+    }
+}