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/models/game_play.go

@@ -33,7 +33,7 @@ type ListGamePlaysQuery struct {
 	GameID     *uuid.UUID `query:"game_id"`
 	CustomerID *uuid.UUID `query:"customer_id"`
 	PrizeID    *uuid.UUID `query:"prize_id"`
-	SortBy     string     `query:"sort_by" validate:"omitempty,oneof=created_at coins_used token_used"`
+	SortBy     string     `query:"sort_by" validate:"omitempty,oneof=created_at coins_used"`
 	SortOrder  string     `query:"sort_order" validate:"omitempty,oneof=asc desc"`
 }