Default to localhost for workstation install

- ConnectionPanel defaults host to localhost, blank username
- Backend OLLAMA_URL defaults to localhost:11434
- Systemd service reads /etc/llm-trainer/env for overrides

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/main.py

@@ -27,7 +27,7 @@ app.add_middleware(
     allow_headers=["*"],
 )
 
-OLLAMA_URL = os.getenv("OLLAMA_URL", "http://192.168.2.47:11434")
+OLLAMA_URL = os.getenv("OLLAMA_URL", "http://localhost:11434")
 
 
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