Fix: Use local astro-orbiter endpoint, not OpenAI API

Set OPENAI_API_BASE_URL (config.py default) to our local vLLM endpoint.
Open WebUI was using hardcoded 'https://api.openai.com/v1' for model discovery.

cluster/applications/open-webui/deployment.yaml

@@ -43,6 +43,8 @@ spec:
         # OLLAMA_BASE_URLS removed: astro-orbiter runs vLLM, not Ollama
         - name: OPENAI_BASE_URL
           value: "http://astro-orbiter:8000/v1"
+        - name: OPENAI_API_BASE_URL
+          value: "http://astro-orbiter:8000/v1"
         - name: OPENAI_API_KEY
           valueFrom:
             secretKeyRef: