Fix category facet so it matches deep subcategories

[Pianczetti]

Questions	Answers
Description?	ps_facetedsearch: fix category facet so it matches deep subcategories (not only direct children). Implemented entirely in module to keep backward compatibility with PS 1.7/8/9. Uses a single subtree-scoped query (nleft/nright) to resolve category names within the current category subtree. Adds a batch multi-name lookup to minimize DB round-trips and a safe BFS fallback when needed.
Type?	bug fix
BC breaks?	no
Deprecations?	no
Fixed ticket?	Fixes PrestaShop/Prestashop#29727.
How to test?	1) Enable ps_facetedsearch and the “Categories” facet. 2) Create a tree: Parent (P) → Child (C) → Grandchild (G). Assign products to all categories 3) Rebuild the module’s index and clear cache. 4) Go to FO category page of P. 5) In the Categories facet, select G. Expected: product list shows only products from G (previously deeper subcategories were not matched).
Sponsor company

[ps-jarvis]

Hello @Pianczetti!

This is your first pull request on ps_facetedsearch repository of the PrestaShop project.

Thank you, and welcome to this Open Source community!

[AmandaIsFive]

Amazing, thank you!! Apparently it works perfectly. I hope they approve your PR soon to improve the module's functionality.