fix: resolve actions/checkout Node.js dependency in Forgejo CI workflow

.forgejo/workflows/deploy-docs.yml

@@ -7,20 +7,20 @@ on:
 
 jobs:
   build-and-deploy:
-    runs-on: docker  # gitea-pages 스택의 runner 가 docker 라벨로 등록됨
-    container:
-      image: python:3.11-bookworm
+    runs-on: docker  # 기본 매핑된 node:20-bookworm 이미지에서 작동
     steps:
       - name: 저장소 체크아웃
         uses: actions/checkout@v4
 
-      - name: Install System Dependencies (Graphviz for FORD)
+      - name: Install Python & Graphviz
         run: |
-          apt-get update
-          apt-get install -y graphviz
+          sudo apt-get update
+          sudo apt-get install -y python3 python3-pip python3-venv graphviz
 
       - name: Install Python Requirements & Compile Docs
         run: |
+          python3 -m venv venv
+          . venv/bin/activate
           pip install -r requirements.txt
           python3 build_docs.py