feat(loyalty): give new balances their expiry

Every lot now gets its expiry when it is created (docs/prd-point-coin.md
F12, PC-502), where it used to never expire until note N4 was settled:

- EARN and an ADJUSTMENT that adds: ComputeExpiry of the organization's
  settings for that currency, from the moment received.
- EXCHANGE_IN: the sooner of the EnakCoin lot's expiry and when EnakPoint
  received now expire (F4).
- PAYMENT_REFUND: the expiry of the lot the EnakPoint came from, but at
  least seven days from the refund (N4, decided). A lot that never expired
  stays so.
- TRANSFER_IN: unchanged, exactly the sender's expiry.

Turning expiry on for a currency for the first time dates every lot of the
organization that still holds something and has no expiry, MIGRATION lots
included, in the same transaction as the setting: a full period from now
when ROLLING, the second fixed date on or after today when FIXED_DATE, so
no customer loses a balance soon after the rule is announced (N4,
decided). Turning it off leaves dated lots as they are. PUT
/marketing/loyalty-settings reports these as expiry_activations (currency,
lots, amount, expires_at); a dry run counts them without dating anything.

The earning processor now also reads the organization settings, and the
wallet admin processor takes the settings reader.

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

internal/repository/loyalty_settings_repository.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"time"
 
 	"github.com/google/uuid"
 	"gorm.io/gorm"
@@ -47,6 +48,12 @@ type LoyaltySettingsRepository interface {
 	InsertChanges(ctx context.Context, changes []entities.LoyaltySettingChange) error
 	// ListChanges returns a page of history, newest first, and the total count.
 	ListChanges(ctx context.Context, filter LoyaltySettingChangeFilter) ([]entities.LoyaltySettingChange, int64, error)
+
+	// UndatedBalance counts an organization's lots of one currency that still hold
+	// something and have no expiry, and what they hold.
+	UndatedBalance(ctx context.Context, organizationID uuid.UUID, currency string) (lots, amount int64, err error)
+	// DateUndatedLots gives those lots an expiry, when expiry is turned on (F12).
+	DateUndatedLots(ctx context.Context, organizationID uuid.UUID, currency string, expiresAt time.Time) (lots, amount int64, err error)
 }
 
 type loyaltySettingsRepository struct {
@@ -174,3 +181,39 @@ func (r *loyaltySettingsRepository) ListChanges(ctx context.Context, filter Loya
 	}
 	return changes, total, nil
 }
+
+func (r *loyaltySettingsRepository) UndatedBalance(ctx context.Context, organizationID uuid.UUID, currency string) (int64, int64, error) {
+	var row struct{ Lots, Amount int64 }
+	err := DBFromContext(ctx, r.db).WithContext(ctx).Raw(`
+		SELECT COUNT(*) AS lots, COALESCE(SUM(remaining_amount), 0) AS amount
+		FROM wallet_lots
+		WHERE organization_id = ? AND currency = ? AND expires_at IS NULL AND remaining_amount > 0`,
+		organizationID, currency).Scan(&row).Error
+	if err != nil {
+		return 0, 0, fmt.Errorf("failed to sum undated wallet lots: %w", err)
+	}
+	return row.Lots, row.Amount, nil
+}
+
+func (r *loyaltySettingsRepository) DateUndatedLots(ctx context.Context, organizationID uuid.UUID, currency string, expiresAt time.Time) (int64, int64, error) {
+	db, err := r.requireTx(ctx)
+	if err != nil {
+		return 0, 0, err
+	}
+	var rows []struct{ RemainingAmount int64 }
+	// Only lots that still hold something: an empty lot never expires anything, and
+	// leaving it undated keeps the history as it was.
+	err = db.Raw(`
+		UPDATE wallet_lots SET expires_at = ?
+		WHERE organization_id = ? AND currency = ? AND expires_at IS NULL AND remaining_amount > 0
+		RETURNING remaining_amount`,
+		expiresAt, organizationID, currency).Scan(&rows).Error
+	if err != nil {
+		return 0, 0, fmt.Errorf("failed to date wallet lots: %w", err)
+	}
+	var amount int64
+	for _, row := range rows {
+		amount += row.RemainingAmount
+	}
+	return int64(len(rows)), amount, nil
+}

internal/repository/loyalty_settings_repository_test.go

@@ -124,7 +124,7 @@ func TestLoyaltySettings_AgainstPostgres(t *testing.T) {
 	orgSettings.PointValue = 200
 	saved := make(chan error, 1)
 	go func() {
-		_, err := p.UpdateOrganization(ctx, org, admin, *orgSettings)
+		_, _, err := p.UpdateOrganization(ctx, org, admin, *orgSettings)
 		saved <- err
 	}()
 	select {