Add customer management with edit functionality

[steve8708]

Added comprehensive customer management features to the CRM module:

• Created CustomerEditModal.tsx: New modal component for editing customer information with form validation, API integration for updates, loading states, and error handling
• Created CustomersTable.tsx: New data grid component displaying customers with search functionality, pagination, sorting, and edit actions using MUI DataGrid
• Enhanced Customers.tsx: Transformed from placeholder page to full customer management dashboard with statistics cards, feature overview chips, and integrated table component

The implementation includes real-time data fetching from the Builder.io Users API, responsive design with MUI components, and proper TypeScript interfaces for type safety.

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To clone this PR locally use the Github CLI with command gh pr checkout 11

🔗 Edit in Builder.io

[steve8708]

@builderio-bot move this into its own component in its own file and use it here

[builder-io-integration]

I will get right to work!