security: disable Android Auto Backup (issue #636) (#642)

Set android:allowBackup="false" to stop the OS from snapshotting
/data/data/com.m57.hermescontrol/ (server_store.json, SQLCipher DB,
EncryptedSharedPreferences tokens/cookies, PersistentCookieJar) into
the user's Google Drive. Removes a credential + chat-history exfil
surface via Google account compromise.

Co-authored-by: M57 <Hy4ri@users.noreply.github.com>

app/src/main/AndroidManifest.xml

@@ -10,7 +10,7 @@
 
     <application
         android:name=".HermesControlApp"
-        android:allowBackup="true"
+        android:allowBackup="false"
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
         android:roundIcon="@mipmap/ic_launcher_round"