BizCore v6.4.3 - Mundo Workspace Scope Lock

SAFE / ADDITIVE PATCH
- Central Mundo administration is locked to the dedicated Mundo Marketplace workspace (code MUNDO).
- Opening a central Mundo admin URL synchronizes the active BizCore workspace to Mundo Marketplace.
- Operating workspaces such as Main Business, Elixora and Infinite Cashew no longer show the central Mundo admin menu.
- Source-workspace product publishing remains available under Inventory -> Publish to Mundo, so product/warehouse ownership is not mixed.
- Mundo Marketplace workspace is marked with commerce + mundo_marketplace control modules.
- Existing seller applications, vendors, products, orders, stock, finance, couriers, payments and API records are preserved.

Install:
1. Upload/extract ZIP over the BizCore domain root (overwrite).
2. Login as Super Admin.
3. Open /update-6.4.3.php
4. Confirm green success.
5. Open Seller Applications: top workspace must show Mundo Marketplace.
6. Switch to Elixora/Infinite Cashew: central Mundo Ecommerce menu should be hidden; Inventory -> Publish to Mundo remains for own products.
