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/customer_points_contract.go

@@ -25,26 +25,6 @@ type PointsHistoryItem struct {
 	CreatedAt   time.Time `json:"created_at"`
 }
 
-type GetCustomerTokensResponse struct {
-	Status  string                         `json:"status"`
-	Message string                         `json:"message"`
-	Data    *GetCustomerTokensResponseData `json:"data,omitempty"`
-}
-
-type GetCustomerTokensResponseData struct {
-	TotalTokens   int64               `json:"total_tokens"`
-	TokensHistory []TokensHistoryItem `json:"tokens_history,omitempty"`
-	LastUpdated   time.Time           `json:"last_updated"`
-}
-
-type TokensHistoryItem struct {
-	ID          string    `json:"id"`
-	Tokens      int64     `json:"tokens"`
-	Type        string    `json:"type"` // EARNED, REDEEMED, EXPIRED
-	Description string    `json:"description"`
-	CreatedAt   time.Time `json:"created_at"`
-}
-
 type GetCustomerWalletResponse struct {
 	Status  string                         `json:"status"`
 	Message string                         `json:"message"`
@@ -53,8 +33,6 @@ type GetCustomerWalletResponse struct {
 
 type GetCustomerWalletResponseData struct {
 	TotalPoints   int64               `json:"total_points"`
-	TotalTokens   int64               `json:"total_tokens"`
 	PointsHistory []PointsHistoryItem `json:"points_history,omitempty"`
-	TokensHistory []TokensHistoryItem `json:"tokens_history,omitempty"`
 	LastUpdated   time.Time           `json:"last_updated"`
 }