Gather optional comment field

Add an optional comment field (“Client Notes”) for each document in the Gather, Upload Documents section. This field allows clients to provide context when a document is not uploaded. Common use cases include noting when the document will become available (e.g., expected issue date) or indicating that the document is prepared internally by our office. This eliminates the misuse of “N/A,” improves tracking of pending items, and reduces follow‑up communication.