Resume last sync

app/src/main/java/eu/faircode/email/EntityAccount.java

@@ -52,6 +52,7 @@ public class EntityAccount {
     public Boolean store_sent; // obsolete
     @NonNull
     public Integer poll_interval; // NOOP interval
+    public Long last_sync;
     public Long seen_until;
     public String state;
     public String error;