feat: 优化 OAuth 账号导入流程

backend/internal/service/openai_token_provider.go

@@ -152,6 +152,12 @@ func (p *OpenAITokenProvider) GetAccessToken(ctx context.Context, account *Accou
 	// 2) Refresh if needed (pre-expiry skew).
 	expiresAt := account.GetCredentialAsTime("expires_at")
 	needsRefresh := expiresAt == nil || time.Until(*expiresAt) <= openAITokenRefreshSkew
+	if needsRefresh && strings.TrimSpace(account.GetOpenAIRefreshToken()) == "" {
+		if expiresAt != nil && !time.Now().Before(*expiresAt) {
+			return "", errors.New("openai access_token expired and refresh_token is missing")
+		}
+		needsRefresh = false
+	}
 	refreshFailed := false
 
 	if needsRefresh && p.refreshAPI != nil && p.executor != nil {