Support custom notes on invoice line items

A use case for invoice manipulation needs per-line-item context on invoices for radon mitigation new construction jobs with multiple repeat visits to the same property. The current workflow in Spectora allows adding custom fees as individual line items and labeling each charge with a unique phase, building, or site location so billing can happen incrementally.

The request is to confirm whether this is currently possible in Attik, or to support a custom note field on individual invoice line items.