fix: resolve emulator crash - thread safety and icon fallback

- NativeSearch: move onResult/onError callbacks outside withContext(Dispatchers.IO) to prevent CalledFromWrongThreadException
- SearchStrategy: change callback types to suspend to enable proper coroutine chaining
- SearchCoordinator: remove leaked CoroutineScope, rely on suspend callback chaining for fallback flow
- Resources: add mipmap-hdpi/mdpi/xhdpi/xxhdpi icon fallbacks for API < 26 devices

gradle.properties

@@ -0,0 +1,4 @@
+org.gradle.jvmargs=-Xmx2048m -Dfile.encoding=UTF-8
+android.useAndroidX=true
+kotlin.code.style=official
+android.nonTransitiveRClass=true