end-to-end CI to match containerization on rest of adipu_server

Dockerfile.backend

@@ -0,0 +1,16 @@
+ARG NODE_VERSION=22-alpine
+FROM node:${NODE_VERSION}
+WORKDIR /app
+
+# Install only production deps using the lockfile so builds are deterministic.
+COPY package.json package-lock.json* ./
+RUN npm ci --omit=dev
+
+# Source. (public/ is served by express.static, so it must be in the image.)
+COPY index.js mailer.js push.js db.js agenda.js ./
+COPY db ./db
+COPY public ./public
+
+EXPOSE 3002
+# Apply the schema (idempotent) then start the server. Same pattern as LabWise.
+CMD ["sh", "-c", "node db/migrate.js && node index.js"]