Implement product variations, enhanced order workflow, mobile responsiveness, and product import system

## Product Variations System
- Add ProductVariation model with quantity-based pricing (1 for £10, 2 for £19, 3 for £25)
- Complete CRUD operations for product variations
- Enhanced ProductService to include variations in all queries
- Updated OrderItem to support ProductVariationId for variation-based orders
- Graceful error handling for duplicate quantity constraints
- Admin interface with variations management (Create/Edit/Delete)
- API endpoints for programmatic variation management

## Enhanced Order Workflow Management
- Redesigned OrderStatus enum with clear workflow states (Accept → Packing → Dispatched → Delivered)
- Added workflow tracking fields (AcceptedAt, PackingStartedAt, DispatchedAt, ExpectedDeliveryDate)
- User tracking for accountability (AcceptedByUser, PackedByUser, DispatchedByUser)
- Automatic delivery date calculation (dispatch date + working days, skips weekends)
- On Hold workflow for problem resolution with reason tracking
- Tab-based orders interface focused on workflow stages
- One-click workflow actions from list view

## Mobile-Responsive Design
- Responsive orders interface: tables on desktop, cards on mobile
- Touch-friendly buttons and spacing for mobile users
- Horizontal scrolling tabs with condensed labels on mobile
- Color-coded status borders for quick visual recognition
- Smart text switching based on screen size

## Product Import/Export System
- CSV import with product variations support
- Template download with examples
- Export existing products to CSV
- Detailed import results with success/error reporting
- Category name resolution (no need for GUIDs)
- Photo URLs import support

## Enhanced Dashboard
- Product variations count and metrics
- Stock alerts (low stock/out of stock warnings)
- Order workflow breakdown (pending, accepted, dispatched counts)
- Enhanced layout with more detailed information

## Technical Improvements
- Fixed form binding issues across all admin forms
- Removed external CDN dependencies for isolated deployment
- Bot Wizard form with auto-personality assignment
- Proper authentication scheme configuration (Cookie + JWT)
- Enhanced debug logging for troubleshooting

## Self-Contained Deployment
- All external CDN references replaced with local libraries
- Ready for air-gapped/isolated network deployment
- No external internet dependencies

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

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

LittleShop/Services/IProductService.cs

@@ -14,4 +14,11 @@ public interface IProductService
     Task<ProductPhotoDto?> AddProductPhotoAsync(CreateProductPhotoDto photoDto);
     Task<bool> RemoveProductPhotoAsync(Guid productId, Guid photoId);
     Task<IEnumerable<ProductDto>> SearchProductsAsync(string searchTerm);
+
+    // Product Variations
+    Task<ProductVariationDto> CreateProductVariationAsync(CreateProductVariationDto createVariationDto);
+    Task<bool> UpdateProductVariationAsync(Guid id, UpdateProductVariationDto updateVariationDto);
+    Task<bool> DeleteProductVariationAsync(Guid id);
+    Task<IEnumerable<ProductVariationDto>> GetProductVariationsAsync(Guid productId);
+    Task<ProductVariationDto?> GetProductVariationByIdAsync(Guid id);
 }