ci: Install Docker 스텝 제거 + version bump

gitea/runner-images:ubuntu-latest 러너 이미지에 Docker가 이미 포함되어
있어 재설치 시도 시 dpkg 충돌 발생. 스텝 제거로 해결.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/build.yaml

@@ -23,17 +23,9 @@ jobs:
     - name: checkout source code
       uses: actions/checkout@v3
 
-    - name: Retrieve version # tag version
+    - name: Retrieve version
       id: img-ver
-      uses: juliangruber/read-file-action@v1
-      with:
-        path: ./version
-
-    - name: Install Docker // Docker 설치
-      run: |
-        curl -fsSL https://get.docker.com -o get-docker.sh
-        sh get-docker.sh        
-      if: runner.os == 'Linux'
+      run: echo "content=$(cat ./version | tr -d '\n')" >> $GITHUB_OUTPUT
 
     - name: Set up Docker Buildx
       # uses: https://github.com/docker/setup-buildx-action@v1