feat: Add first and last name fields to quick entry customer creation

[maasanto]

Problem

When creating a customer of type "Company", users cannot specify the primary contact's first and last name in the quick entry form.
They must navigate to the contact, edit it, go back to the customer, and re-select the primary contact—a confusing and unintuitive process, especially for new users. Small businesses, which rarely need multiple contacts per customer, find this workflow unnecessarily cumbersome.

Solution

This PR adds First Name and Last Name fields to the quick entry form. Users can now specify the primary contact’s name during customer creation, eliminating the need for any additional steps.
The additional fields only appear when the customer type is "Company".

Demo

Key Changes

• Added first_name and last_name fields to the quick entry form.
• Updated contact_address_quick_entry.js, customer.py, and customer.json to support these fields.

Benefits

• Simplified Workflow: No more navigating, editing, or re-selecting contacts.
• Improved Usability: Makes ERPNext more intuitive for new users and small businesses.

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