HTML with PHP Backend for Invoices

I need a simple HTML front-end with PHP backend to create invoices in Invoice Ninja5. This should be pretty simple, you are welcome to use AI to assist in the build of this, I just dont have time. I'm looking for a website that will perform the following: Must load very quickly and feel "light weight" Autocomplete when typing the clients name. (archived or deleted clients should not appear). There will be more than 300 clients It should display the clients Email Address with their name It should then allow for a selection, On-Site or Remote which will ultimately select a different product from Invoice Ninja. If remote, QTY to be entered by per half hour. Half-hour = 1 where as on-site in a 1 hour min but still QTY of 1. If on-site is selected, a mandatory trip fee selection will appear which will pull all products labled Trip Fee* and display their description so the correct one can be selected. We should have an add-on section where a tech can check a box to add Add-On type items to the invoice. These will be linked to Product names inside Invoice Ninja. There should be a notes section that will automatically attach those notes to the invoice. Finally a technician name selection which will also attach the tech name to the invoice notes. When the tech hits submit, it should goto a confirmation page for review. When submitted, it should submit the invoice to InvoiceNinja in a way that has invoice ninja email the invoice to the client for payment. This should be developed in a secure manner that doesnt allow for XSS or ability to query the php directly causing an export of data from Invoice Ninja.