installer: clean platform-cache in finally so failures don't leak

Previous version only deleted platform-cache at the very end of the
success path. If anything between platform install and launcher
profile update failed, the cache jar stuck around. Move the rm into
a finally block so the directory is always cleaned up.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "minecraft-music-quiz-installer",
-  "version": "0.2.2",
+  "version": "0.2.3",
   "description": "마인크래프트 음악퀴즈 간편설치기 + 관리 사이트",
   "main": "dist/installer/main.js",
   "scripts": {