Fix API base path for Hugging Face Spaces nested routes

frontend/src/api/client.js

@@ -1,7 +1,18 @@
-const BASE = ''   // same-origin in prod; Vite proxy handles /api in dev
+const BASE = (() => {
+  if (typeof window === 'undefined') return ''
+  const pathname = window.location.pathname
+  if (pathname.startsWith('/spaces/')) {
+    const parts = pathname.split('/').filter(Boolean)
+    if (parts.length >= 3) {
+      return `/${parts.slice(0, 3).join('/')}`
+    }
+  }
+  return ''
+})()
 
 async function request(path, options = {}) {
-  const res = await fetch(BASE + path, {
+  const url = path.startsWith('/') ? `${BASE}${path}` : `${BASE}/${path}`
+  const res = await fetch(url, {
     credentials: 'include',
     headers: { 'Content-Type': 'application/json', ...(options.headers || {}) },
     ...options,