BizCore v5.6 - Stability Hardening + Mundo Seller Fulfilment

SAFE ADDITIVE UPDATE
- Does not delete or reset existing BizCore/Mundo data.
- Fixes Finance Dashboard ambiguous company_id query.
- Keeps a single non-persistent PDO connection per request and adds one short retry for MySQL connection-limit bursts.
- Returns HTTP 503 with a retry message when the hosting MySQL connection limit is temporarily exhausted.
- Adds seller-specific order fulfilment status without exposing other vendors' orders.
- Seller can mark confirmed marketplace orders: Accepted -> Packing -> Ready to Ship.
- BizCore order view shows each vendor fulfilment state.
- Global Shipped/Delivered updates vendor fulfilment states.

INSTALL
1. Upload/extract this ZIP in the ceylongemx.online root and overwrite matching files.
2. Login as Super Admin.
3. Open: /update-5.6.php
4. Click Install / Repair v5.6 if shown.
5. Test Finance Dashboard and Mundo seller order center.

NOTE
A repeated MySQL 1040/1203 error after this hardening can indicate a hosting-level max_connections limit or load outside this request. The update avoids persistent connections and reduces transient failure impact; it does not alter the server's max_connections setting.
