installer: address vanilla mods preservation, robust map rename, new app icon

Reviewer follow-ups:

1) Preserve mods/ for vanilla packs. `downloadModsFolder` now checks
   `!pack.modsFolder` BEFORE wiping — vanilla packs (no modsFolder) no
   longer clobber a user's hand-curated mods directory. Wipe still runs
   for modded packs to keep different MC versions from colliding.

2) Always rename the extracted map to `saves/<퀴즈이름>/`, regardless of
   the zip's top-level layout. The zip is now extracted into a temp
   directory under saves/, and:
   - if the temp has a single subdirectory, that subdirectory's content
     becomes the world;
   - otherwise the temp dir itself (e.g. level.dat + region/ at root) is
     the world.
   In either case, it is renamed atomically to `saves/<sanitized name>`
   (or `<name>_2` etc. if a user world collides). Marker tracks the
   final folder name for participant cleanup.

User request: replace both .exe icons.

- Added build/icon.ico (multi-size 16/32/48/64/128/256) and build/icon.png
  generated from the new music-note artwork.
- electron-builder.yml: set win.icon, nsis installer/uninstaller icons,
  buildResources=build, include build/icon.* in files for runtime use.
- New electron-builder-rp.yml + dist:win:rp script so the resourcepack
  installer also packages with the same icon.
- BrowserWindow({ icon }) wired in both installer and installer-rp main
  processes so the running window's titlebar/taskbar icon matches.

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

locales/installer/ko-kr.json

@@ -192,8 +192,7 @@
     "skipServerZip": "서버 파일(serverPath)이 비어 있어 서버 zip 다운로드를 건너뜁니다.",
     "skipMapZip": "맵 다운로드를 건너뜁니다 (mapPath 비어 있음 또는 참가자 모드).",
     "cleanupInstallerMap": "이전 설치에서 풀어둔 맵 {{count}}개를 정리합니다.",
-    "mapRenamed": "맵 폴더 이름 변경: {{from}} → {{to}}",
-    "mapRenameFailed": "맵 폴더 이름 변경 실패 ({{from}} → {{to}}): {{message}}",
+    "mapInstalledAs": "맵을 saves/{{name}} 으로 설치했습니다.",
     "clearMods": "기존 mods 폴더({{dir}})를 비우고 새로 받습니다.",
     "skipModsFolder": "modsFolder가 비어 있어 모드 다운로드를 건너뜁니다.",
     "modsIndexFetch": "모드 목록 조회: {{url}}",