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/mappers/spin_game_mapper.go

@@ -36,10 +36,9 @@ func SpinGameResponseDataModelToContract(data *models.SpinGameResponseData) *con
 	}
 
 	return &contract.SpinGameResponseData{
-		GamePlay:        GamePlayResponseModelToContract(&data.GamePlay),
-		PrizeWon:        CustomerGamePrizeResponseModelToContract(data.PrizeWon),
-		CoinsRemaining:  data.CoinsRemaining,
-		TokensRemaining: data.CoinsRemaining,
+		GamePlay:       GamePlayResponseModelToContract(&data.GamePlay),
+		PrizeWon:       CustomerGamePrizeResponseModelToContract(data.PrizeWon),
+		CoinsRemaining: data.CoinsRemaining,
 	}
 }
 
@@ -55,7 +54,6 @@ func GamePlayResponseModelToContract(resp *models.GamePlayResponse) contract.Gam
 		CustomerID: resp.CustomerID,
 		PrizeID:    resp.PrizeID,
 		CoinsUsed:  resp.CoinsUsed,
-		TokenUsed:  resp.CoinsUsed,
 		RandomSeed: resp.RandomSeed,
 		CreatedAt:  resp.CreatedAt,
 		Game:       nil, // Optional field - can be populated separately if needed