Add in-app update checker via Gitea API (v1.0.2)

- Check latest release on startup, show 'update available' dialog with
  Update/ Later buttons
- Download APK with progress and install via ACTION_VIEW + custom
  UpdateFileProvider (no androidx)
- Request unknown-app-sources permission if needed, resume download on
  return to the app

app/build.gradle.kts

@@ -11,8 +11,8 @@ android {
         applicationId = "ru.ua1zbe.svxremote"
         minSdk = 26
         targetSdk = 34
-        versionCode = 2
-        versionName = "1.0.0"
+        versionCode = 4
+        versionName = "1.0.2"
     }
 
     buildTypes {