Use proven Gitea Actions pattern from working workflow

Switch to the pattern that works on other server:
- Run directly on ubuntu-latest (no container)
- Use docker/login-action@v3
- Use docker/setup-buildx-action@v3
- Use docker/build-push-action@v6

This matches the working workflow from another repository
and should work with the Gitea runner configuration.

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

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

.gitea/workflows/build-deploy.yml

@@ -6,34 +6,29 @@ on:
       - main
 
 jobs:
-  build:
+  docker:
     runs-on: ubuntu-latest
-    container:
-      image: docker:24-dind
-      options: --privileged
 
     steps:
       - name: Checkout code
-        run: |
-          apk add --no-cache git
-          git clone https://code.puffinoffset.com/matt/puffin-app.git .
-          git checkout ${{ github.sha }}
+        uses: actions/checkout@v4
 
       - name: Log in to Gitea Container Registry
-        run: |
-          echo "${{ secrets.GITHUB_TOKEN }}" | docker login code.puffinoffset.com -u ${{ github.actor }} --password-stdin
+        uses: docker/login-action@v3
+        with:
+          registry: code.puffinoffset.com
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
 
-      - name: Build Docker image
-        run: |
-          docker build -t code.puffinoffset.com/matt/puffin-app:latest \
-                       -t code.puffinoffset.com/matt/puffin-app:main-${{ github.sha }} \
-                       .
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
 
-      - name: Push Docker images
-        run: |
-          docker push code.puffinoffset.com/matt/puffin-app:latest
-          docker push code.puffinoffset.com/matt/puffin-app:main-${{ github.sha }}
-
-      - name: Show image info
-        run: |
-          docker images | grep puffin-app
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          platforms: linux/amd64
+          push: true
+          tags: |
+            code.puffinoffset.com/matt/puffin-app:latest
+            code.puffinoffset.com/matt/puffin-app:main-${{ github.sha }}