Refactor fetchJson function to use relative paths in the browser and avoid mixed content issues

frontend/lib/api.ts

@@ -2,7 +2,12 @@ const API_BASE =
   process.env.NEXT_PUBLIC_API_URL_INTERNAL || 'http://recipe-api:8080';
 
 export async function fetchJson<T>(path: string, init?: RequestInit): Promise<T> {
-  const res = await fetch(`${API_BASE}${path}`, {
+  // Använd alltid relativ path i webbläsaren för att undvika mixed content
+  const url = typeof window === 'undefined'
+    ? (path.startsWith('http') ? path : `${API_BASE}${path}`)
+    : path;
+
+  const res = await fetch(url, {
     ...init,
     cache: 'no-store',
     headers: {