feat(dingtalk): proactive messaging via Robot OpenAPI + send_message_tool media

- Add DingTalk access-token management (_dingtalk_fetch_access_token,
  _dingtalk_fetch_oapi_token) with process-wide cache, 5 min safety
  margin, and asyncio.Lock for concurrent safety.
- Add _dingtalk_upload_media() — upload local files to /media/upload
  (legacy OAPI token) with mime auto-detection and 20 MB guard.
- Add _dingtalk_classify_chat_id() — route on chat_id shape:
  'cidXXX==' → group /groupMessages/send, plain staffId or
  'user:<staffId>' → 1:1 /oToMessages/batchSend.
- Add dingtalk_send_proactive() orchestrator — text + media delivery.
- In send(), fall back to dingtalk_send_proactive() when no session
  webhook is cached (proactive/cron/cross-platform delivery).
- Fix /sethome DM chat_id: persist 'user:<staffId>' instead of DM
  conversation_id so proactive DM delivery works (gateway/run.py).
- Enhance send_message_tool.py: MEDIA:<path> tag extraction, native
  DingTalk/Feishu routing with media_files support.
- Update test assertions for proactive-send error path.

hermes_cli/dingtalk_auth.py

@@ -30,7 +30,7 @@ REGISTRATION_BASE_URL = os.environ.get(
     "DINGTALK_REGISTRATION_BASE_URL", "https://oapi.dingtalk.com"
 ).rstrip("/")
 
-REGISTRATION_SOURCE = os.environ.get("DINGTALK_REGISTRATION_SOURCE", "openClaw")
+REGISTRATION_SOURCE = os.environ.get("DINGTALK_REGISTRATION_SOURCE", "DING_DWS_CLAW")
 
 
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