fix: rename internal refresh fn to avoid confusion, add Content-Type header

frontend/src/api/client.ts

@@ -2,9 +2,12 @@ import { useAuthStore } from '../store/authStore'
 
 const API_BASE = ''
 
-async function refreshToken(): Promise<boolean> {
+async function _silentRefresh(): Promise<boolean> {
   const res = await fetch(`${API_BASE}/api/auth/refresh`, {
     method: 'POST',
+    headers: {
+      'Content-Type': 'application/json',
+    },
     credentials: 'include',
   })
   if (!res.ok) return false
@@ -28,7 +31,7 @@ export async function apiFetch(path: string, options: RequestInit = {}): Promise
   })
 
   if (res.status === 401) {
-    const refreshed = await refreshToken()
+    const refreshed = await _silentRefresh()
     if (!refreshed) {
       useAuthStore.getState().clearAuth()
       window.location.href = '/login'