Method get_unavailable_reason

src/services/load_balancer.py:317–355

给出更明确的“无可用账号”原因，优先用于分辨率/tier 档位提示。

(
        self,
        *,
        for_image_generation: bool = False,
        for_video_generation: bool = False,
        model: Optional[str] = None,
    )

        ready_candidates = [
            item for item in available_tokens if not item["needs_refresh"]
        ]
        refresh_candidates = [
            item for item in available_tokens if item["needs_refresh"]
        ]
        if ready_candidates and refresh_candidates:
            available_tokens = ready_candidates + refresh_candidates

        debug_logger.log_info("[LOAD_BALANCER] 候选Token负载:")
        for item in available_tokens:
            token = item["token"]
            remaining = "unlimited" if item["remaining"] is None else item["remaining"]
            debug_logger.log_info(
                f"[LOAD_BALANCER]   - Token {token.id} ({token.email}) "
                f"inflight={item['inflight']}, remaining={remaining}, "
                f"needs_refresh={item['needs_refresh']}, credits={token.credits}"
            )

        # 只为候选列表中真正尝试到的 token 做 AT 校验，避免每次请求把所有 token 全扫一遍
        for item in available_tokens:
            token = item["token"]
            token_id = token.id

            token = await self.token_manager.ensure_valid_token(token)
            if not token:
                debug_logger.log_info(
                    f"[LOAD_BALANCER] 跳过 Token {token_id}: AT无效或已过期"
                )
                continue

            if reserve and not await self._reserve_slot(
                token.id, for_image_generation, for_video_generation
            ):
                debug_logger.log_info(
                    f"[LOAD_BALANCER] 跳过 Token {token.id}: 预占槽位失败"
                )
                continue

            if track_pending:
                await self._add_pending(
                    token.id, for_image_generation, for_video_generation
                )