feat(gateway): add WeCom callback-mode adapter for self-built apps

Add a second WeCom integration mode for regular enterprise self-built
applications.  Unlike the existing bot/websocket adapter (wecom.py),
this handles WeCom's standard callback flow: WeCom POSTs encrypted XML
to an HTTP endpoint, the adapter decrypts, queues for the agent, and
immediately acknowledges.  The agent's reply is delivered proactively
via the message/send API.

Key design choice: always acknowledge immediately and use proactive
send — agent sessions take 3-30 minutes, so the 5-second inline reply
window is never useful.  The original PR's Future/pending-reply
machinery was removed in favour of this simpler architecture.

Features:
- AES-CBC encrypt/decrypt (BizMsgCrypt-compatible)
- Multi-app routing scoped by corp_id:user_id
- Legacy bare user_id fallback for backward compat
- Access-token management with auto-refresh
- WECOM_CALLBACK_* env var overrides
- Port-in-use pre-check before binding
- Health endpoint at /health

Salvaged from PR #7774 by @chqchshj.  Simplified by removing the
inline reply Future system and fixing: secrets.choice for nonce
generation, immediate plain-text acknowledgment (not encrypted XML
containing 'success'), and initial token refresh error handling.

gateway/run.py

@@ -1426,6 +1426,7 @@ class GatewayRunner:
                        "MATRIX_ALLOWED_USERS", "DINGTALK_ALLOWED_USERS",
                        "FEISHU_ALLOWED_USERS",
                        "WECOM_ALLOWED_USERS",
+                       "WECOM_CALLBACK_ALLOWED_USERS",
                        "WEIXIN_ALLOWED_USERS",
                        "BLUEBUBBLES_ALLOWED_USERS",
                        "GATEWAY_ALLOWED_USERS")
@@ -1439,6 +1440,7 @@ class GatewayRunner:
                        "MATRIX_ALLOW_ALL_USERS", "DINGTALK_ALLOW_ALL_USERS",
                        "FEISHU_ALLOW_ALL_USERS",
                        "WECOM_ALLOW_ALL_USERS",
+                       "WECOM_CALLBACK_ALLOW_ALL_USERS",
                        "WEIXIN_ALLOW_ALL_USERS",
                        "BLUEBUBBLES_ALLOW_ALL_USERS")
         )
@@ -2043,6 +2045,16 @@ class GatewayRunner:
                 return None
             return FeishuAdapter(config)
 
+        elif platform == Platform.WECOM_CALLBACK:
+            from gateway.platforms.wecom_callback import (
+                WecomCallbackAdapter,
+                check_wecom_callback_requirements,
+            )
+            if not check_wecom_callback_requirements():
+                logger.warning("WeComCallback: aiohttp/httpx not installed")
+                return None
+            return WecomCallbackAdapter(config)
+
         elif platform == Platform.WECOM:
             from gateway.platforms.wecom import WeComAdapter, check_wecom_requirements
             if not check_wecom_requirements():
@@ -2132,6 +2144,7 @@ class GatewayRunner:
             Platform.DINGTALK: "DINGTALK_ALLOWED_USERS",
             Platform.FEISHU: "FEISHU_ALLOWED_USERS",
             Platform.WECOM: "WECOM_ALLOWED_USERS",
+            Platform.WECOM_CALLBACK: "WECOM_CALLBACK_ALLOWED_USERS",
             Platform.WEIXIN: "WEIXIN_ALLOWED_USERS",
             Platform.BLUEBUBBLES: "BLUEBUBBLES_ALLOWED_USERS",
         }
@@ -2148,6 +2161,7 @@ class GatewayRunner:
             Platform.DINGTALK: "DINGTALK_ALLOW_ALL_USERS",
             Platform.FEISHU: "FEISHU_ALLOW_ALL_USERS",
             Platform.WECOM: "WECOM_ALLOW_ALL_USERS",
+            Platform.WECOM_CALLBACK: "WECOM_CALLBACK_ALLOW_ALL_USERS",
             Platform.WEIXIN: "WEIXIN_ALLOW_ALL_USERS",
             Platform.BLUEBUBBLES: "BLUEBUBBLES_ALLOW_ALL_USERS",
         }
@@ -6218,7 +6232,7 @@ class GatewayRunner:
         Platform.TELEGRAM, Platform.DISCORD, Platform.SLACK, Platform.WHATSAPP,
         Platform.SIGNAL, Platform.MATTERMOST, Platform.MATRIX,
         Platform.HOMEASSISTANT, Platform.EMAIL, Platform.SMS, Platform.DINGTALK,
-        Platform.FEISHU, Platform.WECOM, Platform.WEIXIN, Platform.BLUEBUBBLES, Platform.LOCAL,
+        Platform.FEISHU, Platform.WECOM, Platform.WECOM_CALLBACK, Platform.WEIXIN, Platform.BLUEBUBBLES, Platform.LOCAL,
     })
 
     async def _handle_update_command(self, event: MessageEvent) -> str: