Simplify first launch authentication decision (#1685)

We can stop the decision logic even from this place, as we omit the authentication when secrets are not set yet.

ui-lib/src/main/java/co/electriccoin/zcash/ui/preference/StandardPreferenceKeys.kt

@@ -76,5 +76,8 @@ object StandardPreferenceKeys {
             null
         )
     val LATEST_APP_BACKGROUND_TIME_MILLIS =
-        LongPreferenceDefault(PreferenceKey("LATEST_APP_BACKGROUND_TIME_MILLIS"), 0)
+        LongPreferenceDefault(
+            PreferenceKey("LATEST_APP_BACKGROUND_TIME_MILLIS"),
+            Long.MAX_VALUE
+        )
 }