Consider making approval expiration background task configurable by admins

There is a background task that periodically checks for expired approval requests and automatically denies them.

# Background task to check for expired approval requests
def check_expired_approvals():
    """Background task that checks for expired approval requests and auto-denies them"""
    while True:
        try:
            from functions_approvals import auto_deny_expired_approvals
            denied_count = auto_deny_expired_approvals()
            if denied_count > 0:
                print(f"Auto-denied {denied_count} expired approval request(s).")
        except Exception as e:
            print(f"Error in approval expiration check: {e}")
        
        # Check every 6 hours (21600 seconds)
        time.sleep(21600)

The check interval and behavior are currently fixed in code.

Start by locating the background task and the functions_approvals.auto_deny_expired_approvals entry point. Determine how administrators could control the six-hour interval and expiration behavior, then verify that both settings are honored by the approval-expiration task.