feat(feishu): add Feishu inbound webhook, /gh commands and card actions

- add feishu_links D1 table and link store helpers
- implement X-Lark-Signature verification, url_verification, /gh login|logout|comment|merge|close and card.action.trigger Merge/Close
- render interactive cards with clickable title link, inline links and callback buttons (no whole-card card_link)
- bind Feishu account in OAuth callback
- document event subscription and required scopes

docs/guide/logs.md

@@ -11,7 +11,7 @@ Every dispatch attempt is recorded in the D1 `send_logs` table and browsable in
 | `event`      | Event type (e.g. `push`, `pull_request`, `custom`)               |
 | `repo`       | Repository full name (when present)                              |
 | `target`     | Target id the message was sent to                                |
-| `platform`   | `discord` or `telegram`                                          |
+| `platform`   | `discord`, `telegram` or `feishu`                                |
 | `ok`         | Whether the send succeeded                                       |
 | `status`     | HTTP status from the platform API (when applicable)              |
 | `error`      | Error message (when failed)                                      |