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/config.py

@@ -0,0 +1,16 @@
+import os
+
+from pydantic_settings import BaseSettings
+
+
+class Settings(BaseSettings):
+    app_name: str = "sino-mci-channel-service"
+    debug: bool = os.getenv("DEBUG", "false").lower() == "true"
+    host: str = "0.0.0.0"
+    port: int = int(os.getenv("PORT", "8000"))
+    mci_server_url: str = os.getenv("MCI_SERVER_URL", "http://localhost:8080/msg-platform")
+    heartbeat_interval_seconds: int = int(os.getenv("HEARTBEAT_INTERVAL_SECONDS", "30"))
+    pywechat_mock_mode: bool = os.getenv("PYWECHAT_MOCK_MODE", "true").lower() == "true"
+
+
+settings = Settings()