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/Data/LittleShopContext.cs

@@ -13,6 +13,7 @@ public class LittleShopContext : DbContext
     public DbSet<Category> Categories { get; set; }
     public DbSet<Product> Products { get; set; }
     public DbSet<ProductPhoto> ProductPhotos { get; set; }
+    public DbSet<ProductVariation> ProductVariations { get; set; }
     public DbSet<Order> Orders { get; set; }
     public DbSet<OrderItem> OrderItems { get; set; }
     public DbSet<CryptoPayment> CryptoPayments { get; set; }
@@ -52,12 +53,30 @@ public class LittleShopContext : DbContext
                   .HasForeignKey(pp => pp.ProductId)
                   .OnDelete(DeleteBehavior.Cascade);
 
+            entity.HasMany(p => p.Variations)
+                  .WithOne(pv => pv.Product)
+                  .HasForeignKey(pv => pv.ProductId)
+                  .OnDelete(DeleteBehavior.Cascade);
+
             entity.HasMany(p => p.OrderItems)
                   .WithOne(oi => oi.Product)
                   .HasForeignKey(oi => oi.ProductId)
                   .OnDelete(DeleteBehavior.Restrict);
         });
 
+        // ProductVariation entity
+        modelBuilder.Entity<ProductVariation>(entity =>
+        {
+            entity.HasIndex(e => new { e.ProductId, e.Quantity }).IsUnique(); // One variation per quantity per product
+            entity.HasIndex(e => new { e.ProductId, e.SortOrder });
+            entity.HasIndex(e => e.IsActive);
+
+            entity.HasMany(pv => pv.OrderItems)
+                  .WithOne(oi => oi.ProductVariation)
+                  .HasForeignKey(oi => oi.ProductVariationId)
+                  .OnDelete(DeleteBehavior.Restrict);
+        });
+
         // Order entity
         modelBuilder.Entity<Order>(entity =>
         {