Add Dockerfile, compose file and Gitea Actions workflow

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

.gitea/workflows/build.yml

@@ -0,0 +1,47 @@
+name: build
+
+on:
+  push:
+    branches: [main]
+    tags: ["v*"]
+  pull_request:
+
+env:
+  REGISTRY: git.necloud.us
+  IMAGE: git.necloud.us/nate/audiobook-player
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Syntax check
+        run: python3 -m py_compile server.py
+      - name: Check the page script parses
+        run: |
+          python3 - <<'PY'
+          import re
+          open("/tmp/page.js", "w").write(re.search(r"<script>(.*)</script>", open("index.html").read(), re.S).group(1))
+          PY
+          node --check /tmp/page.js
+
+  image:
+    needs: check
+    if: github.event_name != 'pull_request'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Log in to the Gitea container registry
+        run: echo "${{ secrets.REGISTRY_TOKEN }}" | docker login "$REGISTRY" -u "${{ gitea.actor }}" --password-stdin
+      - name: Build
+        run: docker build -t "$IMAGE:${{ gitea.sha }}" -t "$IMAGE:latest" .
+      - name: Smoke test (server refuses to start without accounts, but must import and print usage)
+        run: docker run --rm "$IMAGE:latest" python server.py users
+      - name: Push
+        run: |
+          docker push "$IMAGE:${{ gitea.sha }}"
+          docker push "$IMAGE:latest"
+          if [ "${{ gitea.ref_type }}" = "tag" ]; then
+            docker tag "$IMAGE:latest" "$IMAGE:${{ gitea.ref_name }}"
+            docker push "$IMAGE:${{ gitea.ref_name }}"
+          fi