Add a configuration setting to disable the signature field on printed private billing receipts

Affected users: Medical Office Assistants (MOAs) and clinic administrative staff generating and printing private billing receipts for patients.

Task affected: Patient file > Private billing module. When printing the final private bill/receipt to hand to the patient at checkout.

Impact: Daily occurrence. Patients often assume the signature is mandatory because the line is visible on the printed document, repeatedly asking staff to sign it or attempting to sign it themselves. This leads to unnecessary friction, patient confusion, and wasted administrative time spent explaining that a signature is not required.

Current state: Staff currently leave the signature section blank and must repeatedly clarify to patients that the receipt is valid without a signature.