ci: add Docker build workflow and fix gateway CMD

- Add .github/workflows/build.yml to auto-build and push to Gitea registry
- Change Dockerfile.oauth CMD from "status" to "gateway" for persistent container

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

.github/workflows/build.yml

@@ -0,0 +1,46 @@
+name: Build Nanobot OAuth
+
+on:
+  push:
+    branches: ['main']
+  workflow_dispatch:
+
+env:
+  REGISTRY: git.wylab.me
+  IMAGE_NAME: wylab/nanobot
+  BUILDKIT_PROGRESS: plain
+
+jobs:
+  build:
+    runs-on: [self-hosted, linux-amd64]
+    timeout-minutes: 15
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to the container registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ secrets.REGISTRY_USERNAME || github.actor }}
+          password: ${{ secrets.REGISTRY_PASSWORD || secrets.GITHUB_TOKEN }}
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          file: Dockerfile.oauth
+          provenance: false
+          platforms: linux/amd64
+          cache-from: type=registry,ref=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:buildcache
+          cache-to: type=registry,ref=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:buildcache,mode=max
+          push: true
+          tags: |
+            ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:latest
+            ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.sha }}

Dockerfile.oauth

@@ -8,4 +8,4 @@ COPY nanobot/ /app/nanobot/
 RUN uv pip install --system --no-cache --reinstall /app
 
 ENTRYPOINT ["nanobot"]
-CMD ["status"]
+CMD ["gateway"]