refactor(loyalty): remove what is left of tokens

Tokens are EnakCoin and no app uses the token names any more, so their
compatibility layer goes:

- GET /customer/tokens and its handler, service, processor and response
  types.
- total_tokens and tokens_history on GET /customer/wallet; last_updated
  now comes from the most recent row of either currency.
- token_used and tokens_remaining on game and spin responses, and
  sort_by=token_used on the game play list.
- TOKENS as a campaign type and reward type, with the mapping to COINS:
  migration 000092 already renamed the stored values.

The customer_tokens table and its entity stay, as cmd/wallet-migrate still
reads them, and LEGACY_TOKENS stays as the reference of the MIGRATION rows
it wrote. The docs list the removed names and their replacements.

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

internal/transformer/gamification_transformer.go

@@ -276,7 +276,6 @@ func GamePlayModelToResponse(model *models.GamePlayResponse) *contract.GamePlayR
 		CustomerID: model.CustomerID,
 		PrizeID:    model.PrizeID,
 		CoinsUsed:  model.CoinsUsed,
-		TokenUsed:  model.CoinsUsed,
 		RandomSeed: model.RandomSeed,
 		CreatedAt:  model.CreatedAt,
 		Game:       game,
@@ -306,10 +305,9 @@ func PlayGameModelToResponse(model *models.PlayGameResponse) *contract.PlayGameR
 	}
 
 	return &contract.PlayGameResponse{
-		GamePlay:        gamePlayValue,
-		PrizeWon:        prizeWon,
-		CoinsRemaining:  model.CoinsRemaining,
-		TokensRemaining: model.CoinsRemaining,
+		GamePlay:       gamePlayValue,
+		PrizeWon:       prizeWon,
+		CoinsRemaining: model.CoinsRemaining,
 	}
 }