fix(ci): npm ci → npm install --no-optional (Linux 플랫폼 호환)

macOS ARM64용 @rollup/rollup-darwin-arm64가 package-lock.json에
고정되어 Linux x64 러너에서 EBADPLATFORM 에러 발생.
npm install --no-optional로 플랫폼별 optional dependency를 건너뜀.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/deploy.yml

@@ -25,7 +25,7 @@ jobs:
         env:
           VITE_GOOGLE_CLIENT_ID: ${{ secrets.GOOGLE_CLIENT_ID }}
         run: |
-          npm ci
+          npm install --no-optional
           npx vite build
 
       - name: Deploy frontend