fix(desktop): Persist window size and position across restarts

The desktop window always reset to its default size after restart
because no WindowState was persisted. Add WindowStateStorage backed
by multiplatform-settings (java.util.prefs on desktop) to save and
restore width, height, and position. Use snapshotFlow inside the
Window composition to persist changes continuously, with an explicit
Preferences.flush() to ensure values reach disk before exit.

Also add 'desktop-install' Makefile target to rebuild and copy the
app to /Applications/myicek.app.

Makefile

@@ -1,4 +1,4 @@
-.PHONY: android desktop android-usb android-emulator
+.PHONY: android desktop desktop-install android-usb android-emulator
 
 ADB := $(shell command -v adb 2>/dev/null || echo "$(HOME)/Library/Android/sdk/platform-tools/adb")
 EMULATOR := $(shell command -v emulator 2>/dev/null || echo "$(HOME)/Library/Android/sdk/emulator/emulator")
@@ -11,6 +11,10 @@ android:
 desktop:
 	./gradlew composeApp:run
 
+desktop-install:
+	./gradlew composeApp:packageDistributionForCurrentOS
+	cp -R composeApp/build/compose/binaries/main/app/myicek.app /Applications/myicek.app
+
 android-usb: android
 	$(ADB) -d install -r $(APK)
 	$(ADB) -d shell am start -n ch.parano.myicek/.MainActivity