switch secrets to loading from env - towards a more unified way of handling secrets

frontend/android/app/build.gradle

@@ -65,7 +65,7 @@ android {
     }
 
     defaultConfig {
-        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
+  
         applicationId "com.anydev.anyway"
         // You can update the following values to match your application needs.
         // For more information, see: https://docs.flutter.dev/deployment/android#reviewing-the-gradle-build-configuration.
@@ -77,7 +77,7 @@ android {
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
         // // Placeholders of keys that are replaced by the build system.
-        manifestPlaceholders += ['MAPS_API_KEY': secretProperties.getProperty('MAPS_API_KEY')]
+        manifestPlaceholders += ['MAPS_API_KEY': System.getenv('GOOGLE_MAPS_API_KEY')]
 
     }