fix: use --password-stdin for harbor login

Multiline shell continuation in YAML was causing literal \n in the
command. Single-line pipe also avoids the CLI password warning.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitea/workflows/ci.yaml

@@ -33,10 +33,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - run: |
-          docker login harbor.mymx.me \
-            -u "${{ secrets.HARBOR_USER }}" \
-            -p "${{ secrets.HARBOR_PASS }}"
+      - run: echo "${{ secrets.HARBOR_PASS }}" | docker login harbor.mymx.me -u "${{ secrets.HARBOR_USER }}" --password-stdin
       - run: |
           docker build \
             -t harbor.mymx.me/s5p/s5p:latest \