The per-line item description typed into the row's textarea was never
saved. BaseItemSelect's description field pushes edits out only via an
`update:description` emit, but DocumentItemRow (the single shared row used
by invoices, estimates, and recurring invoices) wired only `@search` and
`@select` — so the emit was dropped and `form.items[index].description`
never updated. On submit the field was lost; a catalog item's description
also reverted on the next re-render.
Capture the event and route it through the existing `updateItemAttribute`
store updater, mirroring how name/quantity/price/discount already sync.
One fix covers all three document types since they share the row.
Also add the missing `items.*.description` nullable rule to
RecurringInvoiceRequest for parity with the invoice/estimate requests.
The backend already persisted and returned description correctly; this was
purely a dropped frontend event.
e41ee8083d