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>

frontend/src/components/ConnectionPanel.jsx

@@ -4,8 +4,8 @@ import { Server, LogIn, LogOut, Key, Eye, EyeOff } from 'lucide-react'
 
 export default function ConnectionPanel({ onConnect, setStatus }) {
   const [form, setForm] = useState({
-    host: '192.168.2.47',
-    username: 'tocmo0nlord',
+    host: 'localhost',
+    username: '',
     password: '',
     key_path: '',
     port: 22,