feat(system): 添加后端初始化和健康检查功能

- 新增后端初始化对话框组件
- 实现后端健康检查和初始化逻辑
- 在 App 组件中集成后端初始化和健康检查
- 新增系统健康检查 API 和相关服务

BillNote_frontend/src/hooks/useCheckBackend.ts

@@ -0,0 +1,52 @@
+import { useEffect, useState } from 'react'
+import request from '@/utils/request'
+
+const MAX_RETRIES = 3
+const RETRY_INTERVAL = 10000 // 10秒
+
+export const useCheckBackend = () => {
+  const [loading, setLoading] = useState(false)
+  const [initialized, setInitialized] = useState(false)
+
+  useEffect(() => {
+    let retries = 0
+
+    const check = async () => {
+      try {
+        await request.get('/sys_health')
+        setInitialized(true)
+        setLoading(false)
+      } catch {
+        if (retries === 0) {
+          // 第一次失败时开始显示加载状态
+          setLoading(true)
+        }
+
+        if (retries < MAX_RETRIES) {
+          retries++
+          setTimeout(check, RETRY_INTERVAL)
+        } else {
+          // 达到重试上限，继续轮询直到后端就绪
+          waitUntilBackendReady()
+        }
+      }
+    }
+
+    const waitUntilBackendReady = async () => {
+      while (true) {
+        try {
+          await request.get('/sys_health')
+          setInitialized(true)
+          setLoading(false)
+          break
+        } catch {
+          await new Promise(res => setTimeout(res, RETRY_INTERVAL))
+        }
+      }
+    }
+
+    check()
+  }, [])
+
+  return { loading, initialized }
+}