feat(loyalty): pay every game with EnakCoin

Games now spend the wallet's EnakCoin instead of the per-type tokens
(docs/prd-point-coin.md F8, K1, PC-403).

GamePlayProcessor.PlayGame charges the game's metadata.coin_cost, 1 when
it is not set; a cost that is not a whole number of at least 1 refuses the
game. In one transaction it picks the prize, takes the EnakCoin with a
GAME_SPEND row pointing at the new game_plays.id (which locks the wallet,
so a customer's plays at the same time queue up), records the play and
takes the prize from stock. The play owns its transaction, so the spin
service no longer wraps it, and the admin play endpoint is now atomic too.

The game, game prize and game play repositories go through DBFromContext
so they join that transaction. DecreaseStock now reports a prize that ran
out (ErrGamePrizeOutOfStock) instead of silently updating nothing; that,
or any other stock failure, cancels the whole play, where it used to be
only printed. The manual AddTokens rollback is gone. Not enough EnakCoin,
an inactive game or a prize that ran out answer 400 on /customer/spin
instead of 500.

game_plays.token_used is renamed coins_used (migration 000095). What a
play costs is no longer the caller's choice, so PlayGameRequest loses
token_used. Responses carry coins_used and coins_remaining; token_used and
tokens_remaining stay as deprecated copies until the apps move over, and
sort_by=token_used still sorts by coins_used.

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

internal/processor/game_play_processor_db_test.go

@@ -0,0 +1,69 @@
+package processor
+
+import (
+	"context"
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"apskel-pos-be/internal/constants"
+	"apskel-pos-be/internal/models"
+	"apskel-pos-be/internal/repository"
+)
+
+// Plays against Postgres, so the game repositories really join the transaction: a
+// refused play leaves no game_plays row and no GAME_SPEND.
+func TestPlayGame_AgainstPostgres(t *testing.T) {
+	db, _, player, _ := walletMoveDB(t)
+	gameID, prizeID := uuid.New(), uuid.New()
+	require.NoError(t, db.Exec(`INSERT INTO games (id, name, type, metadata) VALUES (?, 'Raffle', 'RAFFLE', '{"coin_cost": 2}')`, gameID).Error)
+	require.NoError(t, db.Exec(`INSERT INTO game_prizes (id, game_id, name, weight, stock) VALUES (?, ?, 'Tumbler', 1, 1)`, prizeID, gameID).Error)
+	t.Cleanup(func() {
+		db.Exec(`DELETE FROM wallet_lot_allocations WHERE transaction_id IN (SELECT id FROM wallet_transactions WHERE customer_id = ?)`, player)
+		db.Exec(`DELETE FROM game_plays WHERE game_id = ?`, gameID)
+		db.Exec(`DELETE FROM game_prizes WHERE game_id = ?`, gameID)
+		db.Exec(`DELETE FROM games WHERE id = ?`, gameID)
+	})
+
+	wallet := NewWalletProcessor(repository.NewWalletRepository(db))
+	txm := repository.NewTxManager(db)
+	require.NoError(t, txm.WithTransaction(context.Background(), func(ctx context.Context) error {
+		in := earn(player, 3, nil)
+		in.Currency = constants.WalletCurrencyCoin
+		_, err := wallet.Credit(ctx, in)
+		return err
+	}))
+	p := NewGamePlayProcessor(repository.NewGamePlayRepository(db), repository.NewGameRepository(db), repository.NewGamePrizeRepository(db),
+		wallet, repository.NewWalletQueryRepository(db), txm)
+	play := func() (*models.PlayGameResponse, error) {
+		return p.PlayGame(context.Background(), &models.PlayGameRequest{GameID: gameID, CustomerID: player})
+	}
+
+	res, err := play()
+	require.NoError(t, err)
+	assert.Equal(t, int64(1), res.CoinsRemaining)
+	assert.Equal(t, 2, res.GamePlay.CoinsUsed)
+
+	var spend struct {
+		ReferenceID uuid.UUID
+		Amount      int64
+	}
+	require.NoError(t, db.Raw(`SELECT reference_id, amount FROM wallet_transactions WHERE customer_id = ? AND type = 'GAME_SPEND'`, player).Scan(&spend).Error)
+	assert.Equal(t, res.GamePlay.ID, spend.ReferenceID)
+	assert.Equal(t, int64(-2), spend.Amount)
+
+	// The only prize is gone, then the EnakCoin are too short: neither play leaves a row.
+	_, err = play()
+	assert.ErrorIs(t, err, ErrGamePlayRefused)
+	require.NoError(t, db.Exec(`UPDATE game_prizes SET stock = 5 WHERE id = ?`, prizeID).Error)
+	_, err = play()
+	assert.ErrorIs(t, err, ErrGamePlayRefused)
+
+	var plays, spends int64
+	require.NoError(t, db.Raw(`SELECT COUNT(*) FROM game_plays WHERE game_id = ? AND coins_used = 2`, gameID).Scan(&plays).Error)
+	require.NoError(t, db.Raw(`SELECT COUNT(*) FROM wallet_transactions WHERE customer_id = ? AND type = 'GAME_SPEND'`, player).Scan(&spends).Error)
+	assert.Equal(t, int64(1), plays)
+	assert.Equal(t, int64(1), spends)
+}