Add product variants system and live bot activity dashboard

FEATURES IMPLEMENTED:
1. Product Multi-Buys (renamed from Variations for clarity)
   - Quantity-based pricing deals (e.g., 1 for £10, 3 for £25)
   - Renamed UI to "Multi-Buys" with tags icon for better understanding

2. Product Variants (NEW)
   - Support for colors, flavors, sizes, and other product options
   - Separate from multi-buys - these are the actual variations customers choose
   - Admin UI for managing variants per product
   - Updated OrderItem model to store selected variants as JSON array

3. Live Bot Activity Dashboard
   - Real-time view of customer interactions across all bots
   - Shows active users (last 5 minutes)
   - Live activity feed with user actions
   - Statistics including today's activities and trending products
   - Auto-refreshes every 5 seconds for live updates
   - Accessible via "Live Activity" menu item

TECHNICAL CHANGES:
- Modified OrderItem.SelectedVariant to SelectedVariants (JSON array)
- Added BotActivityController for dashboard endpoints
- Created views for variant management (ProductVariants, CreateVariant, EditVariant)
- Updated Products Index to show separate buttons for Multi-Buys and Variants
- Fixed duplicate DTO definitions (removed duplicate files)
- Fixed ApplicationDbContext reference (changed to LittleShopContext)

UI IMPROVEMENTS:
- Multi-Buys: Tags icon, labeled as "pricing deals"
- Variants: Palette icon, labeled as "colors/flavors"
- Live dashboard with animated activity feed
- Visual indicators for active users and trending products
- Mobile-responsive dashboard layout

This update provides the foundation for:
- Customers selecting variants during checkout
- Real-time monitoring of bot usage patterns
- Better understanding of popular products and user behavior

Next steps: Implement variant selection in TeleBot checkout flow

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

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

LittleShop/Areas/Admin/Views/Shared/_Layout.cshtml

@@ -92,6 +92,11 @@
                                 <i class="fas fa-robot"></i> Bots
                             </a>
                         </li>
+                        <li class="nav-item">
+                            <a class="nav-link" href="@Url.Action("LiveView", "BotActivity", new { area = "Admin" })">
+                                <i class="fas fa-satellite-dish"></i> Live Activity
+                            </a>
+                        </li>
                         <li class="nav-item">
                             <a class="nav-link" href="@Url.Action("Index", "SystemSettings", new { area = "Admin" })">
                                 <i class="fas fa-cog"></i> Settings