Build an internal stock-request web portal (internal store)

I'm looking for a fixed-price quote to build an internal web application for a client: a simplified "internal store" where employees browse available stock and submit requests for equipment, consumables, PPE and tooling, with an approval workflow.
High-level scope:

User accounts with two roles (standard user and store admin), multi-company and multi-site.
Product catalogue: photos, references, stock levels, safety data sheets, search and filters.
Cart and request workflow: create, approve, prepare, "order ready".
Stock management: inbound/outbound, manual adjustments, inventories, low-stock alerts.
Automatic email notifications.
Full history and traceability, admin dashboard, Excel exports.
QR code / barcode scanning, mobile-friendly.

Before I share the full specification, could you confirm: your fixed price and delivery timeline, the tech stack you would use, whether production deployment is included, whether full source code ownership is transferred to me on delivery, the post-delivery bug-fix window, and whether you can sign a short NDA.
I have a detailed spec ready to share once an NDA is in place. Thanks.