fix: use settings.ollama_url instead of hardcoded fallback in cascade router

Fixes #490

src/infrastructure/router/cascade.py

@@ -18,6 +18,8 @@ from enum import Enum
 from pathlib import Path
 from typing import Any
 
+from config import settings
+
 try:
     import yaml
 except ImportError:
@@ -301,7 +303,7 @@ class CascadeRouter:
                 # Can't check without requests, assume available
                 return True
             try:
-                url = provider.url or "http://localhost:11434"
+                url = provider.url or settings.ollama_url
                 response = requests.get(f"{url}/api/tags", timeout=5)
                 return response.status_code == 200
             except Exception as exc: