fix(auth): initialize AuthManager in custom application class (#172)

Closes #68. Redundant initialization in MainActivity has been removed.

app/src/main/AndroidManifest.xml

@@ -8,6 +8,7 @@
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE_REMOTE_MESSAGING" />
 
     <application
+        android:name=".HermesControlApp"
         android:allowBackup="true"
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"