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/clients/pywechat_client.py

@@ -0,0 +1,110 @@
+"""pywechat client abstraction.
+
+The real implementation controls a Windows WeChat PC client via pywechat/pywinauto.
+This module provides a mock adapter for development and testing.
+"""
+
+from __future__ import annotations
+
+import time
+import uuid
+from dataclasses import dataclass, field
+from enum import Enum
+from typing import Optional
+
+
+class LoginStatus(str, Enum):
+    PENDING = "pending"
+    SCANNING = "scanning"
+    SUCCESS = "success"
+    EXPIRED = "expired"
+    FAILED = "failed"
+
+
+class OnlineStatus(str, Enum):
+    OFFLINE = "offline"
+    ONLINE = "online"
+    ERROR = "error"
+
+
+@dataclass
+class WeChatClientState:
+    account_id: str
+    account_name: Optional[str] = None
+    login_status: LoginStatus = LoginStatus.PENDING
+    online_status: OnlineStatus = OnlineStatus.OFFLINE
+    last_heartbeat_at: Optional[float] = None
+    login_id: Optional[str] = None
+    qr_code_url: Optional[str] = None
+    risk_level: int = 0
+    sent_count_today: int = 0
+    error_message: Optional[str] = None
+
+
+class PyWeChatClient:
+    """Mock pywechat client. Replace with real pywechat integration on Windows."""
+
+    def __init__(self, account_id: str, account_name: Optional[str] = None):
+        self.state = WeChatClientState(account_id=account_id, account_name=account_name)
+        self._conversations: dict[str, str] = {}
+
+    def start_login(self) -> str:
+        login_id = str(uuid.uuid4())
+        self.state.login_id = login_id
+        self.state.login_status = LoginStatus.PENDING
+        # In production this would return a real QR code from WeChat.
+        self.state.qr_code_url = f"https://mock.pywechat.qrcode/{login_id}"
+        return login_id
+
+    def confirm_login(self) -> None:
+        self.state.login_status = LoginStatus.SUCCESS
+        self.state.online_status = OnlineStatus.ONLINE
+        self.state.last_heartbeat_at = time.time()
+
+    def expire_login(self) -> None:
+        self.state.login_status = LoginStatus.EXPIRED
+        self.state.online_status = OnlineStatus.OFFLINE
+
+    def heartbeat(self) -> None:
+        self.state.last_heartbeat_at = time.time()
+        if self.state.online_status != OnlineStatus.ERROR:
+            self.state.online_status = OnlineStatus.ONLINE
+
+    def send_text(self, conversation_id: str, text: str) -> dict:
+        """Send a text message to a conversation (group or single chat).
+
+        In production this drives the WeChat PC client UI via pywechat.
+        """
+        self.state.sent_count_today += 1
+        return {
+            "success": True,
+            "message_id": f"mock-msg-{uuid.uuid4().hex[:16]}",
+            "conversation_id": conversation_id,
+            "text_preview": text[:50],
+        }
+
+    def get_state(self) -> WeChatClientState:
+        # Auto-expire login after 5 minutes if not confirmed.
+        if self.state.login_status == LoginStatus.PENDING and self.state.login_id:
+            # mock: auto-confirm after a few seconds for testing
+            pass
+        return self.state
+
+
+class ClientRegistry:
+    def __init__(self):
+        self._clients: dict[str, PyWeChatClient] = {}
+
+    def get_or_create(self, account_id: str, account_name: Optional[str] = None) -> PyWeChatClient:
+        if account_id not in self._clients:
+            self._clients[account_id] = PyWeChatClient(account_id, account_name)
+        return self._clients[account_id]
+
+    def get(self, account_id: str) -> Optional[PyWeChatClient]:
+        return self._clients.get(account_id)
+
+    def list_all(self) -> list[PyWeChatClient]:
+        return list(self._clients.values())
+
+
+registry = ClientRegistry()