Install Docker CLI in workflow before use

Root cause: Gitea act_runner mounts Docker socket but doesn't
include Docker CLI by default to keep the image lightweight.

Solution: Install docker-ce-cli package before running any
docker commands. This allows the workflow to communicate with
the Docker daemon via the mounted socket.

Changes:
- Add step to install Docker CLI from official Docker repository
- Verify installation with docker version
- Continue with login, build, and push steps

Based on Zen expert analysis of the runner environment.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.gitea/workflows/build-deploy.yml

@@ -13,6 +13,20 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v4
 
+      - name: Install Docker CLI
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y ca-certificates curl
+          sudo install -m 0755 -d /etc/apt/keyrings
+          sudo curl -fsSL https://download.docker.com/linux/ubuntu/gpg -o /etc/apt/keyrings/docker.asc
+          sudo chmod a+r /etc/apt/keyrings/docker.asc
+          echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/ubuntu $(. /etc/os-release && echo "$VERSION_CODENAME") stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
+          sudo apt-get update
+          sudo apt-get install -y docker-ce-cli
+
+      - name: Verify Docker installation
+        run: docker version
+
       - name: Log in to Gitea Container Registry
         run: |
           echo "${{ secrets.GITHUB_TOKEN }}" | docker login code.puffinoffset.com -u ${{ github.actor }} --password-stdin