Scaffold Block Seasons Flutter app

flutter create (com.airkjw.blockseasons, iOS+Android), Riverpod,
shared_preferences, audioplayers, gen-l10n EN/KO wiring, app shell
with Home -> Game placeholder.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

android/gradle.properties

@@ -0,0 +1,3 @@
+org.gradle.jvmargs=-Xmx8G -XX:MaxMetaspaceSize=4G -XX:ReservedCodeCacheSize=512m -XX:+HeapDumpOnOutOfMemoryError
+android.useAndroidX=true
+android.enableJetifier=true