fix(feishu): send generated local images to chat

[cswhjiang]

Summary

• add Feishu outbound image support: upload local files to Feishu and send image messages
• keep existing interactive card text sending
• add Feishu-specific media extraction in AgentLoop so replies like 图片已保存：\xxx.png`` automatically attach workspace images

Why

Generated images were saved in workspace but not sent to Feishu chat because outbound media was often missing from the message payload.

Testing

• python compile check for modified files
• local mock tests for Feishu channel: verified interactive + image sending sequence
• local mock tests for AgentLoop: verified filename extraction from assistant response and media propagation to Feishu send path

[chengyongru]

Hi, thank you for your contribution!

This PR has merge conflicts with the main branch that have remained unresolved for an extended period. To keep the repository healthy, we're closing stale PRs with conflicts.

If you're still interested in this feature, please feel free to reopen with the conflicts resolved. We'd be happy to review a fresh PR!