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/processor/game_play_processor.go

@@ -99,10 +99,6 @@ func (p *GamePlayProcessor) ListGamePlays(ctx context.Context, query *models.Lis
 	}
 
 	offset := (query.Page - 1) * query.Limit
-	// The column was renamed; the old name still sorts the same way.
-	if query.SortBy == "token_used" {
-		query.SortBy = "coins_used"
-	}
 
 	// Get game plays from repository
 	gamePlays, total, err := p.gamePlayRepo.List(