fix: resolve Connection Warning on HF by using relative API paths

frontend/lib/api.ts

@@ -18,12 +18,10 @@ export function getAPIBase(): string {
 
   // 2. Hugging Face Space detection (IMPROVED)
   if (hostname.includes('.hf.space')) {
-    // The user prefers to centralize all traffic through their personal REWCHILE backend
-    const backendUrl = `https://rewchile-andesai-backend.hf.space`;
-    
-    console.log('[API] Hugging Face Space detected. Frontend:', hostname);
-    console.log('[API] Connecting to Centralized Backend:', backendUrl);
-    return backendUrl;
+    // On HF Spaces, we use relative paths because we run Nginx as a proxy
+    // to both the frontend and backend in the same container.
+    console.log('[API] Hugging Face Space detected. Using relative paths.');
+    return '';
   }
 
   // 3. Vercel/Production detection