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/contract/game_play_contract.go

@@ -14,13 +14,11 @@ type CreateGamePlayRequest struct {
 }
 
 type GamePlayResponse struct {
-	ID         uuid.UUID  `json:"id"`
-	GameID     uuid.UUID  `json:"game_id"`
-	CustomerID uuid.UUID  `json:"customer_id"`
-	PrizeID    *uuid.UUID `json:"prize_id,omitempty"`
-	CoinsUsed  int        `json:"coins_used"`
-	// Deprecated: the same as CoinsUsed, kept until the apps read coins_used.
-	TokenUsed  int                `json:"token_used"`
+	ID         uuid.UUID          `json:"id"`
+	GameID     uuid.UUID          `json:"game_id"`
+	CustomerID uuid.UUID          `json:"customer_id"`
+	PrizeID    *uuid.UUID         `json:"prize_id,omitempty"`
+	CoinsUsed  int                `json:"coins_used"`
 	RandomSeed *string            `json:"random_seed,omitempty"`
 	CreatedAt  time.Time          `json:"created_at"`
 	Game       *GameResponse      `json:"game,omitempty"`
@@ -35,7 +33,7 @@ type ListGamePlaysRequest struct {
 	GameID     *uuid.UUID `json:"game_id"`
 	CustomerID *uuid.UUID `json:"customer_id"`
 	PrizeID    *uuid.UUID `json:"prize_id"`
-	SortBy     string     `json:"sort_by" validate:"omitempty,oneof=created_at coins_used token_used"`
+	SortBy     string     `json:"sort_by" validate:"omitempty,oneof=created_at coins_used"`
 	SortOrder  string     `json:"sort_order" validate:"omitempty,oneof=asc desc"`
 }
 
@@ -58,6 +56,4 @@ type PlayGameResponse struct {
 	GamePlay       GamePlayResponse   `json:"game_play"`
 	PrizeWon       *GamePrizeResponse `json:"prize_won,omitempty"`
 	CoinsRemaining int64              `json:"coins_remaining"`
-	// Deprecated: the same as CoinsRemaining, kept until the apps read coins_remaining.
-	TokensRemaining int64 `json:"tokens_remaining"`
 }