SetupEncryptionActivity: give transparent background to make it more seamless

Signed-off-by: Álvaro Brey <alvaro.brey@nextcloud.com>

app/src/main/AndroidManifest.xml

@@ -196,6 +196,7 @@
             android:exported="false" />
         <activity
             android:name=".ui.activity.SetupEncryptionActivity"
+            android:theme="@style/Theme.NoBackground"
             android:exported="false" />
         <activity
             android:name=".ui.activity.ContactsPreferenceActivity"

app/src/main/res/values/styles.xml

@@ -342,6 +342,15 @@
         <item name="windowNoTitle">true</item>
     </style>
 
+    <style name="Theme.NoBackground" parent="Theme.ownCloud.Toolbar">
+        <item name="android:windowIsTranslucent">true</item>
+        <item name="android:windowBackground">@android:color/transparent</item>
+        <item name="android:windowContentOverlay">@null</item>
+        <item name="android:windowNoTitle">true</item>
+        <item name="android:windowIsFloating">true</item>
+        <item name="android:backgroundDimEnabled">false</item>
+    </style>
+
     <!-- Text styles -->
     <style name="NextcloudTextAppearanceHeadline" parent="@style/TextAppearance.AppCompat.Headline">
         <item name="android:textSize">26sp</item>