feat(账号): 添加 Sora 账号双表同步与创建

- 新增 sora_accounts 表与 accounts.extra GIN 索引\n- OpenAI OAuth 支持同时创建 Sora 账号并同步配置\n- Token 刷新同步关联 Sora 账号凭证与扩展表\n- 增加 Sora 账号连通性测试与前端开关文案

backend/internal/service/account_service_delete_test.go

@@ -54,6 +54,10 @@ func (s *accountRepoStub) GetByCRSAccountID(ctx context.Context, crsAccountID st
 	panic("unexpected GetByCRSAccountID call")
 }
 
+func (s *accountRepoStub) FindByExtraField(ctx context.Context, key string, value interface{}) ([]Account, error) {
+	panic("unexpected FindByExtraField call")
+}
+
 func (s *accountRepoStub) Update(ctx context.Context, account *Account) error {
 	panic("unexpected Update call")
 }