Fix: CI에서 actions/checkout도 제거 — 모든 GitHub Action 의존 완전 제거

Gitea runner가 github.com clone에서 멈추는 문제.
actions/checkout@v4도 git fetch로 직접 대체.

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

.github/workflows/ci.yml

@@ -11,7 +11,13 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - name: Checkout
+        run: |
+          git config --global --add safe.directory /workspace/A301/a301_client
+          git init
+          git remote add origin $GITHUB_SERVER_URL/$GITHUB_REPOSITORY.git
+          git fetch --depth=1 origin $GITHUB_SHA
+          git checkout $GITHUB_SHA
 
       - name: Setup Node.js
         run: |
@@ -41,7 +47,13 @@ jobs:
     if: github.event_name == 'push' && github.ref == 'refs/heads/main'
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - name: Checkout
+        run: |
+          git config --global --add safe.directory /workspace/A301/a301_client
+          git init
+          git remote add origin $GITHUB_SERVER_URL/$GITHUB_REPOSITORY.git
+          git fetch --depth=1 origin $GITHUB_SHA
+          git checkout $GITHUB_SHA
 
       - name: Login to Gitea Registry
         run: echo "${{ secrets.GITEA_TOKEN }}" | docker login git.tolelom.xyz -u "${{ github.actor }}" --password-stdin