Fix production auth by proxying /api to backend in remote builds.

Remote frontend nginx now forwards API requests to Django so login and registration work when the host proxy only routes to port 8080.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/lib/api/errors.js

@@ -1,6 +1,14 @@
 export function formatApiErrorData(data) {
   if (!data) return ''
-  if (typeof data === 'string' && data.trim()) return data.trim()
+  if (typeof data === 'string' && data.trim()) {
+    const text = data.trim()
+    if (text.startsWith('<') && text.includes('</html>')) {
+      const title = text.match(/<title>([^<]+)<\/title>/i)?.[1]?.trim()
+      if (title) return title
+      return 'Сервер вернул HTML вместо JSON. Проверьте проксирование /api на backend.'
+    }
+    return text
+  }
   if (typeof data?.detail === 'string' && data.detail.trim()) return data.detail.trim()
   if (Array.isArray(data?.non_field_errors) && data.non_field_errors.length) {
     return data.non_field_errors.join('; ')