fix model warning and use openwebui for preference based router demo

demos/use_cases/preference_based_routing/arch_config.yaml

@@ -1,7 +1,7 @@
 version: "0.1-beta"
 
 routing:
-  model: gpt-4o
+  model: archgw-v1-router-model
 
 listeners:
   egress_traffic:
@@ -14,7 +14,7 @@ llm_providers:
 
   - name: archgw-v1-router-model
     provider_interface: openai
-    model: cotran2/llama-4-epoch
+    model: cotran2/qwen-4-epoch-2600
     base_url: http://34.46.85.85:8000/v1
 
   - name: gpt-4o

demos/use_cases/preference_based_routing/docker-compose.yaml

@@ -1,17 +1,14 @@
 services:
 
-  chatbot_ui:
-    build:
-      context: ../../shared/chatbot_ui
-      dockerfile: Dockerfile
+  open-web-ui:
+    image: ghcr.io/open-webui/open-webui:main
+    restart: always
     ports:
-      - "18080:8080"
+      - "8080:8080"
     environment:
-      - CHAT_COMPLETION_ENDPOINT=http://host.docker.internal:12000/v1
-    extra_hosts:
-      - "host.docker.internal:host-gateway"
-    volumes:
-      - ./arch_config.yaml:/app/arch_config.yaml
+      - DEFAULT_MODEL=gpt-4o-mini
+      - ENABLE_OPENAI_API=true
+      - OPENAI_API_BASE_URL=http://host.docker.internal:12000/v1
 
   jaeger:
     build:

demos/use_cases/preference_based_routing/test_router_endpoint.rest

@@ -1,10 +1,10 @@
 @arch_llm_router_endpoint = http://35.192.87.187:8000
 
-POST {{arch_llm_router_endpoint}}/v1/chat/completions HTTP/1.1
+POST http://34.46.85.85:8000/v1/chat/completions HTTP/1.1
 Content-Type: application/json
 
 {
-  "model": "cotran2/llama-1b-4-26",
+  "model": "cotran2/qwen-4-epoch-2600",
   "messages": [
     {
       "role": "user",