mobile: drop ACCESS_BACKGROUND_LOCATION from the manifest

[aojea]

What

Removes android.permission.ACCESS_BACKGROUND_LOCATION from the Android manifest. ACCESS_COARSE_LOCATION, FOREGROUND_SERVICE_LOCATION and the service's foregroundServiceType="location" stay.

Why

Play Console flagged the permission on the first AAB upload and asked for a background-location declaration ("Let us know why your app accesses location in the background").

The app does not need it:

• The only location feature is the opt-in get_location tool in MainActivity.kt, which reads getLastKnownLocation(NETWORK_PROVIDER) and rounds it to ~1 km.
• It only ever requests ACCESS_COARSE_LOCATION at runtime; ACCESS_BACKGROUND_LOCATION was never requested, so no user was prompted for "Allow all the time" and nothing depended on it.
• The node runs in SamNodeForegroundService, started from the activity with foregroundServiceType="location" when coarse location is granted. Android counts location reads made while such a service is running as foreground access, which is exactly the "agent queries the phone in your pocket" case.

Play's policy says apps that access location via a foreground service do not need ACCESS_BACKGROUND_LOCATION, and the declaration form is triggered by the manifest entry alone. Background-location approval also requires the feature to be core to the app plus a demo video, which an optional sensor toggle would not satisfy.

Zero behavior change. The next AAB built from this drops the "undeclared Location permissions" block in the console; ACCESS_COARSE_LOCATION only needs to be reflected in the Data safety section.

[gemini-code-assist]

Code Review

This pull request removes the ACCESS_BACKGROUND_LOCATION permission from the Android manifest file and adds an explanatory comment clarifying that location services are handled via a foreground service. I have no feedback to provide as there are no review comments and the changes are straightforward.