feat(shop-sales): ledger contracts + docs for consumer PSP sales tracking

platform/order + platform/event gain the sale.paid and refund.issued wire
contracts (per-rate VatBuckets, PSP provider, timestamps) that drive the
ledger's SHOP-/REFUND- vouchers (go-cart-actor 2b819bd). docs/status.md
records the shop-sales + PSP settlement stack (tickets 17 + 18); the
wayfinder ledger tracker gains the two closed tickets and their Decisions
entries. Bumps go-cart-actor + backoffice (PSP float stat).

🤖 Generated with Codebuff
Co-Authored-By: Codebuff <noreply@codebuff.com>

order/order.go

@@ -137,3 +137,51 @@ func DecodeInvoiceCredited(raw []byte) (InvoiceCredited, error) {
 	return c, err
 }
 
+// SalePaid is the payload of an event.SalePaid envelope: a consumer (PSP)
+// order was captured. It is the accounting fact for shop sales — the ledger
+// aggregates captured sales into the daily SHOP- voucher (clearing D /
+// 304x C per rate / 261x C per rate). Invoice orders never emit it (they book
+// via invoice.issued).
+//
+// PaymentMethod is the PSP provider name (e.g. "stripe", "klarna"), carried
+// from the order's payment record. CapturedAtMs is the capture moment — the
+// ledger keys the daily voucher on its UTC date (fakturametoden: capture date
+// decides the VAT period).
+type SalePaid struct {
+	OrderID       string      `json:"order_id"`
+	PaymentMethod string      `json:"payment_method,omitempty"`
+	AmountIncVat  int64       `json:"amount_inc_vat"`
+	VatBuckets    []VatBucket `json:"vat_buckets,omitempty"`
+	CapturedAtMs  int64       `json:"captured_at_ms"`
+}
+
+func (s SalePaid) Encode() ([]byte, error) { return json.Marshal(s) }
+
+func DecodeSalePaid(raw []byte) (SalePaid, error) {
+	var s SalePaid
+	err := json.Unmarshal(raw, &s)
+	return s, err
+}
+
+// RefundIssued is the payload of an event.RefundIssued envelope: a refund was
+// issued against a captured PSP order. The amount and per-rate VAT split are
+// pro-rated from the order's captured sale (line-level return mapping is out
+// of scope). The ledger books the reversal voucher (clearing C / 304x D /
+// 261x D per rate), idempotent per RefundID (the provider refund reference,
+// unique per refund). Invoice orders reverse via invoice.credited instead.
+type RefundIssued struct {
+	OrderID      string      `json:"order_id"`
+	RefundID     string      `json:"refund_id"`
+	AmountIncVat int64       `json:"amount_inc_vat"`
+	VatBuckets   []VatBucket `json:"vat_buckets,omitempty"`
+	RefundedAtMs int64       `json:"refunded_at_ms"`
+}
+
+func (r RefundIssued) Encode() ([]byte, error) { return json.Marshal(r) }
+
+func DecodeRefundIssued(raw []byte) (RefundIssued, error) {
+	var r RefundIssued
+	err := json.Unmarshal(raw, &r)
+	return r, err
+}
+