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/wallet_query_processor_test.go

@@ -122,7 +122,6 @@ func TestWalletQueryProcessor_SummaryShowsWhereEachRowCameFromOrWent(t *testing.
 
 	// The pre-wallet fields are still filled, from the wallet.
 	assert.Equal(t, int64(250), data.TotalPoints)
-	assert.Equal(t, int64(8), data.TotalTokens)
 	require.Len(t, data.PointsHistory, 2)
 	assert.Equal(t, int64(-50), data.PointsHistory[0].Points)
 	assert.Equal(t, constants.WalletTxTypePayment, data.PointsHistory[0].Type)
@@ -174,12 +173,6 @@ func TestWalletQueryProcessor_LegacyEndpointsSplitByCurrency(t *testing.T) {
 	assert.Equal(t, int64(100), points.TotalPoints)
 	require.Len(t, points.PointsHistory, 1)
 	assert.Equal(t, int64(100), points.PointsHistory[0].Points)
-
-	tokens, err := p.LegacyTokens(context.Background(), uuid.New())
-	require.NoError(t, err)
-	assert.Equal(t, int64(8), tokens.TotalTokens)
-	require.Len(t, tokens.TokensHistory, 1)
-	assert.Equal(t, int64(8), tokens.TokensHistory[0].Tokens)
 }
 
 func TestWalletQueryProcessor_TransactionsQuery(t *testing.T) {