mobile: drop ACCESS_BACKGROUND_LOCATION from the manifest

The permission was declared but never requested at runtime, so no user
was ever prompted for it and nothing depended on it. get_location reads
the network provider's last known position from inside the foreground
service, which is declared with foregroundServiceType="location"; Android
treats that as foreground access while the node runs off-screen, and it
needs only ACCESS_COARSE_LOCATION.

Play Console flagged the declared-but-unused permission and asked for a
background-location declaration, which an optional sensor toggle would
not pass. Removing it makes the form moot.

Author: aojea

mobile/sam-node-app/android/app/src/main/AndroidManifest.xml

@@ -1,7 +1,9 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android">
     <uses-permission android:name="android.permission.INTERNET"/>
+    <!-- Coarse only, and no ACCESS_BACKGROUND_LOCATION: get_location is served
+         from the foreground service (type "location"), which Android counts as
+         foreground access while the node runs off-screen. -->
     <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
-    <uses-permission android:name="android.permission.ACCESS_BACKGROUND_LOCATION"/>
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE"/>
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE_CONNECTED_DEVICE"/>
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE_LOCATION"/>