ci(gitea): add workflow for publishing Docker images

Adds Gitea CI/CD workflow that builds and pushes Docker images to the registry on tag push or manual trigger.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

.gitea/workflows/publish-image.yml

@@ -0,0 +1,47 @@
+name: Publish image
+
+on:
+  push:
+    tags:
+      - '*'
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: Image tag to publish (only used for manual runs)
+        required: false
+        default: manual
+
+jobs:
+  build-and-push:
+    runs-on: ready2blob-image
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Resolve image tag
+        id: vars
+        run: |
+          if [ "${{ github.ref_type }}" = "tag" ]; then
+            echo "tag=${{ github.ref_name }}" >> "$GITHUB_OUTPUT"
+          else
+            echo "tag=${{ inputs.tag }}" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Log in to git.azuze.fr registry
+        uses: docker/login-action@v3
+        with:
+          registry: git.azuze.fr
+          username: ${{ gitea.actor }}
+          password: ${{ secrets.REGISTRY_TOKEN }}
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          push: true
+          tags: |
+            git.azuze.fr/kawa/ready2blob:${{ steps.vars.outputs.tag }}
+            git.azuze.fr/kawa/ready2blob:latest