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/processor/loyalty_settings_processor_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"os"
 	"testing"
+	"time"
 
 	"github.com/google/uuid"
 	"github.com/stretchr/testify/assert"
@@ -29,6 +30,9 @@ type loyaltyRepoFake struct {
 	orgValues    map[string]string
 	changes      []entities.LoyaltySettingChange
 	locks        []uuid.UUID
+	// Lots without an expiry per currency: how many and what they hold.
+	undated map[string][2]int64
+	dated   map[string]time.Time
 }
 
 func (f *loyaltyRepoFake) GetOutletValues(context.Context, uuid.UUID) (map[string]string, error) {
@@ -263,7 +267,7 @@ func TestLoyaltySettings_UpdateOrganization(t *testing.T) {
 	settings.CoinExpiry.Enabled = true
 	settings.CoinExpiry.Unit = constants.LoyaltyExpiryUnitDay
 
-	changes, err := p.UpdateOrganization(ctx, org, admin, *settings)
+	changes, _, err := p.UpdateOrganization(ctx, org, admin, *settings)
 	require.NoError(t, err)
 	keys := []string{}
 	for _, c := range changes {
@@ -316,7 +320,7 @@ func TestLoyaltySettings_UpdateRejectsInvalidValues(t *testing.T) {
 		s, err := p.Organization(ctx, org)
 		require.NoError(t, err)
 		mutate(s)
-		_, err = p.UpdateOrganization(ctx, org, uuid.New(), *s)
+		_, _, err = p.UpdateOrganization(ctx, org, uuid.New(), *s)
 		assert.ErrorIs(t, err, ErrInvalidLoyaltySettings, name)
 	}
 	assert.Empty(t, repo.changes, "nothing is written when a value is invalid")
@@ -330,3 +334,52 @@ func TestLoyaltySettings_UpdateRejectsInvalidValues(t *testing.T) {
 	_, err = p.UpdateOutlet(ctx, org, uuid.New(), uuid.New(), *s)
 	assert.ErrorIs(t, err, repository.ErrLoyaltyOutletNotFound)
 }
+
+func (f *loyaltyRepoFake) UndatedBalance(_ context.Context, _ uuid.UUID, currency string) (int64, int64, error) {
+	u := f.undated[currency]
+	return u[0], u[1], nil
+}
+
+func (f *loyaltyRepoFake) DateUndatedLots(_ context.Context, _ uuid.UUID, currency string, expiresAt time.Time) (int64, int64, error) {
+	u := f.undated[currency]
+	if f.dated == nil {
+		f.dated = map[string]time.Time{}
+	}
+	f.dated[currency] = expiresAt
+	delete(f.undated, currency)
+	return u[0], u[1], nil
+}
+
+// Turning expiry on dates the balances that had none, a full cycle away; a dry run
+// only counts them, and saving again dates nothing more.
+func TestLoyaltySettings_TurningExpiryOnDatesExistingBalances(t *testing.T) {
+	org, admin := uuid.New(), uuid.New()
+	repo := &loyaltyRepoFake{undated: map[string][2]int64{"POINT": {3, 1500}, "COIN": {2, 40}}}
+	p := NewLoyaltySettingsProcessor(repo, txRunnerFake{})
+	p.now = func() time.Time { return time.Date(2026, 11, 20, 3, 0, 0, 0, time.UTC) }
+	ctx := context.Background()
+
+	settings, err := p.Organization(ctx, org)
+	require.NoError(t, err)
+	settings.PointExpiry.Enabled = true
+
+	_, preview, err := p.PreviewOrganization(ctx, org, *settings)
+	require.NoError(t, err)
+	require.Len(t, preview, 1)
+	assert.Equal(t, "POINT", preview[0].Currency)
+	assert.Equal(t, int64(1500), preview[0].Amount)
+	assert.Empty(t, repo.dated, "a dry run dates nothing")
+
+	_, activations, err := p.UpdateOrganization(ctx, org, admin, *settings)
+	require.NoError(t, err)
+	require.Len(t, activations, 1)
+	assert.Equal(t, int64(3), activations[0].Lots)
+	// Default FIXED_DATE on 31 Dec: the second one after 20 Nov 2026.
+	assert.Equal(t, "2027-12-31", activations[0].ExpiresAt.In(walletDisplayLocation).Format("2006-01-02"))
+	assert.Equal(t, activations[0].ExpiresAt, repo.dated["POINT"])
+	assert.NotContains(t, repo.dated, "COIN", "EnakCoin expiry stays off")
+
+	_, again, err := p.UpdateOrganization(ctx, org, admin, *settings)
+	require.NoError(t, err)
+	assert.Empty(t, again, "already on: nothing is activated twice")
+}