installer-rp: ship installer/styles.css so packaged UI renders

The rp installer's `index.html` references `../installer/styles.css`,
which works in dev because both source directories sit side by side.
The packaged exe's `files` list only included `installer-rp/**`, so
inside the asar the stylesheet path resolved to nothing and the UI
rendered completely unstyled (per user screenshot).

Add the single shared file `installer/styles.css` to the rp build's
file list. The cross-directory `<link>` reference now resolves inside
the asar, and we avoid duplicating the stylesheet.

Bump to 0.1.1 — small patch-level fix.

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

package.json

@@ -1,6 +1,6 @@
 {
   "name": "minecraft-music-quiz-installer",
-  "version": "0.1.0",
+  "version": "0.1.1",
   "description": "마인크래프트 음악퀴즈 간편설치기 + 관리 사이트",
   "main": "dist/installer/main.js",
   "scripts": {