Initial gitea-mcpo-docker image

Wraps the official gitea-mcp server (binary copied from
docker.gitea.com/gitea-mcp-server:1.7.0) and serves it two ways from one
container:

- :8000 mcpo (OpenAPI) for Open WebUI, using the container's service
  token and guarded by MCPO_API_KEY.
- :8080 native streamable-HTTP MCP at /mcp for coding agents, with the
  service token stripped so each client must send its own Gitea token.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitea/workflows/docker-build.yml

@@ -0,0 +1,42 @@
+name: Build and push image
+
+on:
+  push:
+    branches:
+      - main
+  workflow_dispatch:
+
+env:
+  IMAGE: code.aneur.in/cloud/gitea-mcpo-docker
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to code.aneur.in registry
+        uses: docker/login-action@v3
+        with:
+          registry: code.aneur.in
+          username: ${{ gitea.actor }}
+          password: ${{ secrets.BUILD_API_TOKEN }}
+
+      - name: Promote current "latest" to "previous"
+        run: |
+          if docker buildx imagetools inspect "$IMAGE:latest" >/dev/null 2>&1; then
+            docker buildx imagetools create -t "$IMAGE:previous" "$IMAGE:latest"
+          else
+            echo "No existing :latest to promote; skipping."
+          fi
+
+      - name: Build and push
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          push: true
+          tags: code.aneur.in/${{ gitea.repository }}:latest