fix: use configured backend_url for API base instead of /api path

- Read HF_BACKEND_BASE_URL from localStorage in api client
- Refresh baseURL on each request interceptor
- Persist backend_url from wizard config during app bootstrap
- Persist backend_base_url after setup save

src/services/api.ts

@@ -1,10 +1,15 @@
 import axios from 'axios'
 
+const getApiBase = () => {
+  return localStorage.getItem('HF_BACKEND_BASE_URL') || import.meta.env.VITE_API_BASE || 'http://127.0.0.1:8000'
+}
+
 const api = axios.create({
-  baseURL: import.meta.env.VITE_API_BASE || '/api',
+  baseURL: getApiBase(),
 })
 
 api.interceptors.request.use((config) => {
+  config.baseURL = getApiBase()
   const token = localStorage.getItem('token')
   if (token) {
     config.headers.Authorization = `Bearer ${token}`