fix: restore brainstorming feature with missing socket server and real-time events

memento-note/Dockerfile.socket

@@ -0,0 +1,23 @@
+FROM node:22-bookworm-slim
+
+WORKDIR /app
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    openssl \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY package.json package-lock.json* ./
+RUN npm install
+
+# We only need the socket server and dependencies
+COPY socket-server.ts ./
+COPY tsconfig.json ./
+
+# Environment defaults
+ENV NODE_ENV=production
+ENV SOCKET_PORT=3002
+ENV SOCKET_HTTP_PORT=3003
+
+# Run with tsx (included in devDependencies but we need it at runtime here)
+# Alternatively, we could build it to JS, but tsx is easier for this standalone file.
+CMD ["npx", "tsx", "socket-server.ts"]