feat(loyalty): show what an order earned on the order and receipt

Adds points_earned and coins_earned to the order response
(docs/prd-point-coin.md F3, PC-205). The POS prints the receipt from this
response, so the receipt gets them too.

The values are the sums of the order's EARN rows, read in one query for a
list of orders. They are filled for create, add items, update, detail and
list, and are 0 for an order that earned nothing. UpdateOrder earns before
building its response, so a payment completed there already shows the
earning. A failure to read them is logged and leaves them at 0 rather than
failing the order read. The self-order session listing reads orders
directly from the repository and still shows 0.

The two order hooks are merged into one OrderLoyalty interface (paid,
refunded, earned by orders) with a single SetLoyalty.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/repository/earning_repository.go

@@ -59,6 +59,9 @@ type EarningRepository interface {
 	ReversalRequested(ctx context.Context, earnTransactionID uuid.UUID) (int64, error)
 	// LotIDsCreatedBy returns the lots a credit created.
 	LotIDsCreatedBy(ctx context.Context, transactionID uuid.UUID) ([]uuid.UUID, error)
+	// EarnedByOrders sums the EARN rows of each order per currency, as
+	// map[order]map[currency]amount. Orders that earned nothing are absent.
+	EarnedByOrders(ctx context.Context, orderIDs []uuid.UUID) (map[uuid.UUID]map[string]int64, error)
 }
 
 type earningRepository struct {
@@ -232,3 +235,35 @@ func (r *earningRepository) LotIDsCreatedBy(ctx context.Context, transactionID u
 	}
 	return out, nil
 }
+
+func (r *earningRepository) EarnedByOrders(ctx context.Context, orderIDs []uuid.UUID) (map[uuid.UUID]map[string]int64, error) {
+	earned := map[uuid.UUID]map[string]int64{}
+	if len(orderIDs) == 0 {
+		return earned, nil
+	}
+	var rows []struct {
+		OrderID  string
+		Currency string
+		Amount   int64
+	}
+	err := DBFromContext(ctx, r.db).WithContext(ctx).Raw(`
+		SELECT reference_id::text AS order_id, currency, SUM(amount) AS amount
+		FROM wallet_transactions
+		WHERE reference_type = ? AND type = ? AND reference_id IN ?
+		GROUP BY reference_id, currency`,
+		constants.WalletRefTypeOrder, constants.WalletTxTypeEarn, orderIDs).Scan(&rows).Error
+	if err != nil {
+		return nil, fmt.Errorf("failed to sum earnings of orders: %w", err)
+	}
+	for _, row := range rows {
+		id, err := uuid.Parse(row.OrderID)
+		if err != nil {
+			continue
+		}
+		if earned[id] == nil {
+			earned[id] = map[string]int64{}
+		}
+		earned[id][row.Currency] = row.Amount
+	}
+	return earned, nil
+}