Add Gitea Actions CI: test + build/push image on main

Tests on every push/PR; on main, builds and pushes
git.jpaul.io/justin/ag-bids-mcp:{latest,sha} to the Gitea registry. The .0.2
act_runner has the host docker.sock mounted, so plain docker build/push work.
Watchtower on .0.2 then auto-deploys :latest within ~5 min.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -0,0 +1,45 @@
+name: CI
+
+# Test on every push/PR; build + push the image only on main.
+# The act_runner on .0.2 has the host docker.sock mounted (DOCKER_HOST is
+# preset), so plain `docker build`/`docker push` work with no DinD setup.
+# Watchtower on .0.2 auto-pulls git.jpaul.io/justin/ag-bids-mcp:latest within
+# ~5 min, so a successful push here is the whole deploy.
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+env:
+  IMAGE: git.jpaul.io/justin/ag-bids-mcp
+
+jobs:
+  test:
+    runs-on: docker
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install + run tests
+        run: |
+          python3 -m pip install --quiet --upgrade pip
+          python3 -m pip install --quiet -r requirements.txt pytest
+          python3 -m pytest -q
+
+  build-push:
+    needs: test
+    if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+    runs-on: docker
+    steps:
+      - uses: actions/checkout@v4
+      # Auth to the Gitea container registry. The auto-provisioned job token
+      # works for the repo owner's package namespace in the common config; if a
+      # run ever fails here with a permissions error, add a repo Actions secret
+      # REGISTRY_TOKEN (a PAT with write:package) and swap secrets.GITHUB_TOKEN
+      # for secrets.REGISTRY_TOKEN below.
+      - name: Log in to registry
+        run: echo "${{ secrets.GITHUB_TOKEN }}" | docker login git.jpaul.io -u "${{ github.actor }}" --password-stdin
+      - name: Build + push
+        run: |
+          docker build -t "$IMAGE:latest" -t "$IMAGE:${{ github.sha }}" .
+          docker push "$IMAGE:latest"
+          docker push "$IMAGE:${{ github.sha }}"