feat: Initial Docker Compose setup for conversation layer

Adds a docker-compose.yml to manage the OpenWA, Chat UI, and WhatsApp Router services.

Includes:
- Dockerfile and basic Node.js skeleton for Chat UI.
- Dockerfile and basic Node.js skeleton for WhatsApp Router.
- docker-compose.yml defining the three services, including:
    - Placeholder for OpenWA image (you must configure this).
    - Build contexts for UI and router.
    - Port mappings.
    - Environment variable examples.
    - Volume for OpenWA session persistence.
- Updated README.md with detailed setup, configuration, and usage instructions.

chat-ui/Dockerfile

@@ -0,0 +1,20 @@
+# Use an official Node.js runtime as a parent image
+FROM node:18-slim
+
+# Set the working directory in the container
+WORKDIR /usr/src/app
+
+# Copy package.json and package-lock.json (or yarn.lock)
+COPY package*.json ./
+
+# Install application dependencies
+RUN npm install
+
+# Bundle app source
+COPY . .
+
+# Expose the port the app runs on
+EXPOSE 3000
+
+# Define the command to run the app
+CMD [ "node", "server.js" ]