Release cleanup: remove unused state, harden service, add proguard rules

- Remove unused serviceRunning state variable
- Guard unregisterReceiver against double-call
- Add proguard rules for OkHttp, Coroutines, Play Services, WorkManager
- Remove empty drawable directory

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/src/main/java/com/example/helios_location_finder/ListenerService.kt

@@ -39,8 +39,10 @@ class ListenerService : Service() {
     }
 
     override fun onDestroy() {
-        unregisterReceiver(receiver)
-        Log.d(TAG, "Listener service stopped, receiver unregistered")
+        try {
+            unregisterReceiver(receiver)
+        } catch (_: IllegalArgumentException) { }
+        Log.d(TAG, "Listener service stopped")
         super.onDestroy()
     }
 

app/src/main/java/com/example/helios_location_finder/MainActivity.kt

@@ -50,7 +50,6 @@ class MainActivity : ComponentActivity() {
 
     private val foregroundGranted = mutableStateOf(false)
     private val backgroundGranted = mutableStateOf(false)
-    private val serviceRunning = mutableStateOf(false)
 
     private val foregroundPermissionLauncher = registerForActivityResult(
         ActivityResultContracts.RequestMultiplePermissions()
@@ -154,7 +153,6 @@ class MainActivity : ComponentActivity() {
             }
         }
         ListenerService.start(this)
-        serviceRunning.value = true
     }
 }