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.

whatsapp-router/package.json

@@ -0,0 +1,12 @@
+{
+  "name": "whatsapp-router",
+  "version": "1.0.0",
+  "description": "WhatsApp Router for OpenWA and LLM Agent",
+  "main": "router.js",
+  "scripts": {
+    "start": "node router.js"
+  },
+  "dependencies": {
+    "express": "^4.17.1"
+  }
+}