fix(dingtalk): support picture/image message inbound

[MrTreasure]

DingTalk 渠道图片消息支持

变更

1. import 新增: bytes/encoding/json/io/net/http/os/path/filepath/time, media
2. struct 加字段: tokenMu, accessToken, tokenExpires (OpenAPI token 缓存)
3. onChatBotMessageReceived: 支持图片消息, 优雅降级
4. 新增方法: getAccessToken, downloadInboundPicture, keysOf, stringValue

说明

• 图片消息走 downloadInboundPicture 下载并存入 MediaStore
• 任意步骤失败优雅降级（返回 nil, nil），不阻塞文字链路
• OpenAPI token 缓存 ~2h，提前 120s 过期

[github-actions]

This PR has had no activity for 7 days and has been marked as stale. If you are still working on it, please push an update or leave a comment; otherwise it will be closed automatically in 7 days.

[MrTreasure]

Status update: this fix is still actively maintained and is part of the current local deployment. I have synced with the current upstream master and rerun the targeted DingTalk channel tests; the inbound picture/image handling path passes locally. The branch remains mergeable, and I am available to address any review feedback.

[github-actions]

This PR has had no activity for 7 days and has been marked as stale. If you are still working on it, please push an update or leave a comment; otherwise it will be closed automatically in 7 days.

[github-actions]

This PR has been closed after 14 days of inactivity. If you would like to continue, feel free to reopen it or submit a new PR.