fix(profile): stop passkey load error toast when feature is disabled

The PASSKEY_DISABLED silence guard compared the string error code
against error.code, but the api client puts the numeric envelope code
there and the string code in error.reason, so the guard never matched
and every /profile visit on deployments without WebAuthn configured
showed a spurious "failed to load passkeys" toast.

Read error.reason instead, and skip the credentials request entirely
when the feature is disabled so the card no longer issues a request
that is guaranteed to fail with 403.

frontend/src/components/user/profile/ProfilePasskeyCard.vue

@@ -205,12 +205,18 @@ function extractErrorMessage(error: unknown, fallback: string): string {
 }
 
 async function loadCredentials(): Promise<void> {
+  if (!props.enabled) {
+    credentials.value = []
+    return
+  }
   loading.value = true
   try {
     credentials.value = await passkeyAPI.list()
   } catch (error) {
-    const code = (error as { code?: string }).code
-    if (code !== 'PASSKEY_DISABLED') {
+    // 字符串错误码在 reason 字段（code 是数字状态码）；
+    // 设置变更竞态下后端仍可能返回 PASSKEY_DISABLED，静默处理
+    const reason = (error as { reason?: string }).reason
+    if (reason !== 'PASSKEY_DISABLED') {
       appStore.showError(t('profile.passkey.loadFailed'))
     }
   } finally {