feat: Webhook integration for team notifications (Feishu/WeChat Work)

Feature Request

Summary

Add webhook support to notify team members via Feishu (Lark) or WeChat Work (WeCom) when certain events occur in TeamAI.

Use Case

Our team uses Feishu/WeChat Work as the primary communication tool. We want to:

1. Track team activity - Know when colleagues push/pull resources
2. Monitor skill usage - Understand which skills are being used
3. Session visibility - Get notified when team members start/stop AI sessions

Proposed Solution

Add webhook configuration in teamai.yaml:

sharing:
  webhooks:
    enabled: true
    endpoints:
      - url: https://open.feishu.cn/open-apis/bot/v2/hook/xxx
        type: feishu
        events: [push, pull, skill-use, session-start, session-stop]
      - url: https://qyapi.weixin.qq.com/cgi-bin/webhook/send?key=xxx
        type: wecom
        events: [push, pull]

Events to Support

Questions for Maintainers

1. Is this feature aligned with the project direction?
2. Should webhook be a built-in feature or a plugin?
3. Any preferred event naming convention?

Start by reviewing the proposed sharing.webhooks configuration in teamai.yaml and the listed push, pull, skill-use, session-start, and session-stop events. Resolve whether this belongs in the core or a plugin, define the event naming and Feishu/WeCom payload requirements, and confirm the maintainers’ direction before implementation.