feat(channel-service): add Python FastAPI pywechat channel service

- Add FastAPI project under channel-service/
- Implement mock pywechat client adapter (login, send, heartbeat)
- Add /v1/wechat-personal/login/*, /v1/wechat-personal/send/* APIs
- Add /v1/heartbeat and /v1/monitor/status for client health
- Add /monitor HTML page with Web Components
- Add pytest suite and Dockerfile
- Update .gitignore for Python/Node artifacts

channel-service/app/services/send_service.py

@@ -0,0 +1,33 @@
+from __future__ import annotations
+
+from app.clients.pywechat_client import ClientRegistry, OnlineStatus, registry
+
+
+class SendService:
+    def __init__(self, registry: ClientRegistry):
+        self.registry = registry
+
+    def send_text(self, account_id: str, conversation_id: str, text: str) -> dict:
+        client = self.registry.get(account_id)
+        if client is None:
+            return {"success": False, "error": f"account {account_id} not registered"}
+        if client.state.online_status != OnlineStatus.ONLINE:
+            return {"success": False, "error": "account not online"}
+        return client.send_text(conversation_id, text)
+
+    def send_image(self, account_id: str, conversation_id: str, image_url: str) -> dict:
+        # Placeholder for image sending via pywechat.
+        client = self.registry.get(account_id)
+        if client is None:
+            return {"success": False, "error": f"account {account_id} not registered"}
+        if client.state.online_status != OnlineStatus.ONLINE:
+            return {"success": False, "error": "account not online"}
+        return {
+            "success": True,
+            "message_id": f"mock-img-{image_url.split('/')[-1]}",
+            "conversation_id": conversation_id,
+            "type": "image",
+        }
+
+
+send_service = SendService(registry)