refactor: 统一接口调用为单前缀写法，去除 19 处页面内写死的 /mp-api（API_BASE 已含），并新增 check:api-prefix 防回归脚本

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/packages/user/pages/card-notice.vue

@@ -23,7 +23,7 @@ const loading = ref(true)
 
 onMounted(async () => {
   try {
-    const list = await post<any[]>('/mp-api/mpContent/queryList', { channel: 'pingxiang', type: 'CARD_NOTICE' })
+    const list = await post<any[]>('/mpContent/queryList', { channel: 'pingxiang', type: 'CARD_NOTICE' })
     content.value = list?.[0]?.content || ''
   } catch {
     showToast('加载失败')