feat(config): integrate etcd for service discovery and config management

- Add etcd-client dependency for distributed configuration storage
- Implement EtcdConfig with priority: etcd > environment variables > defaults
- Add ServiceRegistry for service registration with lease keep-alive
- Integrate etcd-based service discovery for appks gRPC connections
- Add service watcher for real-time service instance updates
- Migrate Redis configuration from single URL to cluster node list
- Update Dockerfile with default IMKS_HOST and IMKS_PORT environment variables
- Add etcd bootstrap configuration through environment variables
- Implement Redis cluster URL building with optional authentication

Dockerfile

@@ -30,9 +30,9 @@ RUN useradd -m -u 1000 imks && chown -R imks:imks /app
 USER imks
 
 ENV IMKS_HOST=0.0.0.0
-ENV IMKS_PORT=3000
+ENV IMKS_PORT=50048
 
-EXPOSE 3000
+EXPOSE 50048
 
 HEALTHCHECK --interval=15s --timeout=3s --start-period=10s --retries=3 \
     CMD curl -sf http://localhost:3000/health || exit 1