fix: set correct proxy headers in nginx and VITE_API_URL to fix 400 Bad Request

frontend/nginx.conf

@@ -45,6 +45,10 @@ server {
 
     location /api/ {
         proxy_pass http://backend:8000/api/;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
     }
 
 }