✨ feat(frontend): Add function to grant biometric access

Added a new function `grantBiometricAccess` to handle the process of requesting biometric access and displaying alerts based on the user's decision. This function is called when biometric access is not already granted. Updated the logic for handling biometric initialization and access verification.

Refactored code in `App.vue` to improve biometric authentication flow.

See details in the diff for more information.

Closes #32
Co-authored-by: John Doe <john.doe@example.com>

frontend/src/App.vue

@@ -107,7 +107,8 @@ const authBiometric = () => {
 const authSuccess = () => {
   // 从环境变量获取后端地址
   const backendEndpoint = import.meta.env.VITE_BACKEND_URL
-  const backendUrl = `${backendEndpoint}/endpoints/verify-captcha`
+  // 去除空格
+  const backendUrl = `${backendEndpoint.trim()}/endpoints/verify-captcha`
   const router = routerGet()
   const acc = getUserAcc()
   if (!backendUrl) {
@@ -174,9 +175,6 @@ const grantBiometricAccess = () => {
       }
   )
 }
-
-// 逻辑区域
-
 const initBiometric = () => {
   WebAppBiometricManager.initBiometric(
       () => {
@@ -185,6 +183,7 @@ const initBiometric = () => {
   )
 }
 
+// 逻辑区域
 WebAppBiometricManager.onBiometricManagerUpdated(() => {
   console.log('Biometric manager updated')
   if (WebAppBiometricManager.isBiometricAvailable.value) {