feat: add history sync worker

app/src/main/java/com/bitcointxoko/gudariwallet/api/Models.kt

@@ -1,6 +1,7 @@
 package com.bitcointxoko.gudariwallet.api
 
 import com.google.gson.TypeAdapter
+import com.google.gson.annotations.JsonAdapter
 import com.google.gson.annotations.SerializedName
 import com.google.gson.stream.JsonReader
 import com.google.gson.stream.JsonToken
@@ -205,7 +206,8 @@ data class PaymentRecord(
 
 data class PaymentExtra(
     @SerializedName("tag")            val tag: String?,
-    @SerializedName("comment")        val comment: String?,
+    @JsonAdapter(FlexibleStringAdapter::class)
+    val comment: String?,
     @SerializedName("success_action") val successAction: SuccessAction?,
     @SerializedName("wallet_id")      val walletId: String?,
     @SerializedName("destination")    val destination: String?,
@@ -308,4 +310,10 @@ data class WsPayment(
 data class FiatRateResponse(
     val rate: Double,   // sat to fiat rate
     val price : Double  // BTC price in the requested fiat currency
-)
+)
+
+// ── History sync ─────────────────────────────────────────────────────────────
+data class PaginatedPaymentsResponse(
+    @SerializedName("data")  val data:  List<PaymentRecord>,
+    @SerializedName("total") val total: Int
+)