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/entities/campaign.go

@@ -16,27 +16,6 @@ const (
 	CampaignTypeMixed  CampaignType = "MIXED"
 )
 
-// legacyCampaignTokens is what COINS was called before tokens became EnakCoin
-// (docs/prd-point-coin.md §10). Requests may still send it; it is stored as COINS.
-const legacyCampaignTokens = "TOKENS"
-
-// NormalizeCampaignType maps the legacy TOKENS to COINS and leaves anything else as is.
-func NormalizeCampaignType(t string) CampaignType {
-	if t == legacyCampaignTokens {
-		return CampaignTypeCoins
-	}
-	return CampaignType(t)
-}
-
-// NormalizeCampaignRewardType maps the legacy TOKENS to COINS and leaves anything
-// else as is.
-func NormalizeCampaignRewardType(t string) CampaignRewardType {
-	if t == legacyCampaignTokens {
-		return CampaignRewardTypeCoins
-	}
-	return CampaignRewardType(t)
-}
-
 type RuleType string
 
 const (

internal/entities/campaign_test.go

@@ -1,18 +0,0 @@
-package entities
-
-import (
-	"testing"
-
-	"github.com/stretchr/testify/assert"
-)
-
-func TestNormalizeCampaignTypesMapsLegacyTokensToCoins(t *testing.T) {
-	assert.Equal(t, CampaignTypeCoins, NormalizeCampaignType("TOKENS"))
-	assert.Equal(t, CampaignTypeCoins, NormalizeCampaignType("COINS"))
-	assert.Equal(t, CampaignTypePoints, NormalizeCampaignType("POINTS"))
-	assert.Equal(t, CampaignType(""), NormalizeCampaignType(""), "an empty filter stays empty")
-
-	assert.Equal(t, CampaignRewardTypeCoins, NormalizeCampaignRewardType("TOKENS"))
-	assert.Equal(t, CampaignRewardTypeReward, NormalizeCampaignRewardType("REWARD"))
-	assert.Equal(t, CampaignRewardType(""), NormalizeCampaignRewardType(""))
-}