feat: able to display token billing stat via billing api (close #186)

common/constants.go

@@ -18,7 +18,8 @@ var Logo = ""
 var TopUpLink = ""
 var ChatLink = ""
 var QuotaPerUnit = 500 * 1000.0 // $0.002 / 1K tokens
-var DisplayInCurrencyEnabled = false
+var DisplayInCurrencyEnabled = true
+var DisplayTokenStatEnabled = true
 
 var UsingSQLite = false