fix teacher, parent and admin pages

src/api/http.ts

@@ -37,7 +37,17 @@ export async function apiFetch<T>(
     headers.set('Authorization', `Bearer ${token}`)
   }
 
-  const res = await fetch(apiUrl(path), { ...init, headers })
+  const url = apiUrl(path)
+  let res: Response
+  try {
+    res = await fetch(url, { ...init, headers })
+  } catch (e) {
+    const hint = import.meta.env.DEV
+      ? ' Start the API and ensure Vite can reach it (see vite.config.ts; default proxy is http://192.168.3.100:8000).'
+      : ''
+    const reason = e instanceof Error ? e.message : 'Failed to fetch'
+    throw new ApiHttpError(`Network error: ${reason}.${hint}`, 0, null)
+  }
   const body: unknown = await res.json().catch(() => null)
 
   if (!res.ok) {