Background Product Cache Reloads for Massive Catalog Performance

We have refactored the product caching architecture to support very large catalogs (hundreds of thousands of products) without cold-cache reloads in the storefront runtime. Product cache reloads (including Redis reloads and forced cache reloads from the admin panel) now run in the background, so storefront performance remains unaffected. In some scenarios, changes may become visible with a short delay, once product preloading has completed. This update affects products only.