Add Gitea Actions workflow to build and publish Docker image

Builds on push to main and publishes to git.sdgarren.com container registry.
Requires REGISTRY_USERNAME and REGISTRY_TOKEN repo secrets.

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

.gitea/workflows/docker-publish.yaml

@@ -0,0 +1,45 @@
+name: Docker Build and Publish
+
+on:
+  push:
+    branches: [ "main" ]
+    paths-ignore:
+      - '**/README.md'
+  workflow_dispatch:
+
+jobs:
+  build-and-push-docker-image:
+    name: Build Docker image and publish to Gitea
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+      id-token: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup Docker buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Login to Gitea Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: git.sdgarren.com
+          username: ${{ secrets.REGISTRY_USERNAME }}
+          password: ${{ secrets.REGISTRY_TOKEN }}
+
+      - name: Build and push Docker image
+        id: build-and-push
+        uses: docker/build-push-action@v5
+        with:
+          provenance: false
+          context: .
+          platforms: linux/amd64
+          push: true
+          tags: |
+            git.sdgarren.com/scott/usb-crash-cart:latest
+
+      - name: Image digest
+        run: echo ${{ steps.build-and-push.outputs.digest }}