Sale Credit Approval

This module extends the Approvals module to support a dedicated Credit Customer Approval flow. Key features:

• New approval type option: "Require Credit Approval for Sale Orders"
• Partners (customers) gain a credit approval state: draft / pending / approved / refused / expired
• Attempting to confirm a sale order for a credit customer whose approval is not in the approved state raises a clear user error.
• Credit approval expiry date: auto-sets partner state to "expired".
• Smart button on the partner form showing linked approval requests.
• Smart button on the sale order showing the customer's credit status.
• Dedicated menu under Approvals ▶ Credit Approvals.
• Email notification to salesperson on approval/refusal.
• Configurable: which approval type triggers the check (set on the type).