feat: Initialize backend API server with S2A proxy, mail service management, team processing, and add frontend email configuration page.

backend/internal/api/team_process.go

@@ -258,6 +258,7 @@ func processSingleTeam(idx int, req TeamProcessRequest) TeamProcessResult {
 	if owner.AccountID != "" {
 		// 直接使用数据库中存储的 account_id
 		teamID = owner.AccountID
+		inviter.SetAccountID(teamID) // 必须设置到 inviter 中
 		logger.Info(fmt.Sprintf("%s 使用已存储的 Team ID: %s", logPrefix, teamID), owner.Email, "team")
 	} else {
 		// 如果没有存储，才请求 API 获取

backend/internal/invite/team.go

@@ -54,6 +54,11 @@ func NewWithProxy(accessToken, proxy string) *TeamInviter {
 	}
 }
 
+// SetAccountID 手动设置 account_id（当已有存储值时使用）
+func (t *TeamInviter) SetAccountID(accountID string) {
+	t.accountID = accountID
+}
+
 // GetAccountID 获取 Team 的 account_id (workspace_id)
 func (t *TeamInviter) GetAccountID() (string, error) {
 	req, _ := http.NewRequest("GET", "https://chatgpt.com/backend-api/accounts/check/v4-2023-04-27", nil)