Allow accounts to record partial/advance payments against a PO before
full delivery. A new PARTIALLY_PAID status tracks in-progress payment;
paidAmount accumulates across multiple markPaid calls. PO only closes
when both paidAmount >= totalAmount AND all line items are delivered.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
qtyChanged/priceChanged/nameChanged were tracked for the diff view but
gstChanged was missing, so an edited GST % showed only the new value
with no strikethrough of the old one. Added gstChanged detection and
two-line rendering (old % struck through, new % in amber) to match the
other diff columns.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
parseFloat('0') is falsy in JS so `|| 0.18` silently discarded the user's
explicit 0% selection. Replaced with an explicit empty-string guard.
Adds e2e spec gst-rate.spec.ts covering all five GST rates (0/5/12/18/28%).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
