onst formData = new FormData(document.getElementById('invoiceSettingsForm'));
    
    const settings = {
        invoiceNumberPrefix: formData.get('invoiceNumberPrefix'),
        invoiceNumberFormat: formData.get('invoiceNumberFormat'),
        defaultPaymentTerms: parseInt(formData.get('defaultPaymentTerms')),
        defaultTaxRate: parseFloat(formData.get('defaultTaxRate')),
        autoCalculateRentalDays: formData.get('autoCalculateRentalDays') === 'on',
        showLogoOnInvoice: formData.get('showLo