MS-245/Optimize product listing performance with new ProductCardDTO and server-side filtering

Summary

This MR introduces a major performance optimization for product listing pages by eliminating N+1 queries and moving filtering logic to the server.

Changes

New Types

• ProductCardDTO: Optimized DTO with flattened category data and preOrderAuthorization
• ProductCardSearchParams: Parameters for the new search endpoint
• FilterCountsDTO: Dynamic counts for filters (in stock, on sale)
• ProductCardPageResponse: Paginated response with filter counts

API Changes

• Added searchProductCards() function calling /api/stock/products/cards/search
• Updated getProductByCategory() to return Page<ProductCardDTO>
• Updated getRelatedProducts() to return ProductCardDTO[]

Component Updates

• ProductCard: Removed API call, uses props directly for availability
• ProductListed: Updated props to include preOrderAuthorization
• ProductsView: Added skeleton loaders, uses ProductCardDTO
• ProductFilterCard: Added keyword search with debounce, filter counts display, reset button
• ProductSearchByCategory/PageView: Unified implementation with new API
• ProductSearchByNamePageView: Unified implementation with new API
• RelatedProducts: Updated to use ProductCardDTO
• ProductGridList: Updated to use ProductCardDTO
• ProductSection: Updated to use ProductCardDTO

Performance Improvements

• Eliminated N+1 query problem (was: 1 + N API calls, now: 1 API call)
• Server-side filtering reduces client-side processing
• Debounced inputs prevent excessive API calls

UX Improvements

• Skeleton loaders during loading state
• Dynamic filter counts show available options
• Unified availability display across grid and list views

Breaking Changes

• ProductCard props changed: now requires preOrderAuthorization instead of fetching internally
• Components using CustomProductRequest for listings should migrate to ProductCardDTO

Testing

• Verify product listing pages load correctly
• Test all filter combinations (price, on sale, in stock, keyword)
• Verify pagination works correctly
• Test grid/list view toggle
• Verify availability badge shows correctly

Backend Requirements

• New endpoint: GET /api/stock/products/cards/search with query parameters
• Endpoint should return ProductCardPageResponse with filter counts

Related Issues

Closes MS-245