BizCore v4.0.1 HOTFIX

Fixes:
1. Production v4.0 incorrectly queried a non-existent `products` table.
   BizCore inventory actually uses `items`, with `item_name`, and workspace
   assignment through `item_workspaces`.
2. Header navigation variables for Bank Accounts, Bank Transfers,
   Reconciliation, Statement Import, Cash Flow, Cheques and Production are now
   always initialized before the navigation renders, removing PHP warnings.

INSTALL:
- Upload ZIP to the same BizCore project root.
- Extract > Overwrite.
- Open https://ceylongemx.online/update-4.0.1.php
- Click Apply / Verify Hotfix.
- Ctrl + F5.
- Open Production > Production Dashboard.

You do NOT need to rerun update-4.0.php if v4.0 already installed successfully.
