Initial MCM project: FastAPI + Textual TUI unified messenger

MultiCustomerMessenger supporting Telegram (python-telegram-bot),
WhatsApp (Green API) and SMS (python-gsmmodem-new). REST API with
Bearer-token auth, SQLAlchemy models for MariaDB, APScheduler for
background polling, and Textual TUI running in same asyncio event-loop.

install/mcm.service

@@ -0,0 +1,24 @@
+[Unit]
+Description=MCM – MultiCustomerMessenger API
+Documentation=https://gitea.it-drui.de/viewit/MCM
+After=network-online.target mariadb.service
+Wants=network-online.target
+
+[Service]
+Type=simple
+User=pi
+Group=pi
+WorkingDirectory=/opt/mcm
+EnvironmentFile=/opt/mcm/.env
+ExecStart=/opt/mcm/.venv/bin/python main_api_only.py
+Restart=on-failure
+RestartSec=5
+StandardOutput=journal
+StandardError=journal
+SyslogIdentifier=mcm
+
+# Modem-Gerät Zugriff
+SupplementaryGroups=dialout
+
+[Install]
+WantedBy=multi-user.target