Initial commit: Gitea Actions demo project with Docker build

Add simple Node.js Hello World application with automated Docker build and
push workflow using Gitea Actions. The workflow builds and pushes images to
the Gitea registry with versioning from package.json.

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

Dockerfile

@@ -0,0 +1,11 @@
+FROM node:18-alpine
+
+WORKDIR /app
+
+COPY package*.json ./
+
+RUN npm install --production
+
+COPY index.js ./
+
+CMD ["node", "index.js"]