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.

tasks/receiver.py

@@ -0,0 +1,39 @@
+from __future__ import annotations
+
+import logging
+from typing import TYPE_CHECKING
+
+from apscheduler.schedulers.asyncio import AsyncIOScheduler
+from apscheduler.triggers.interval import IntervalTrigger
+
+if TYPE_CHECKING:
+    from channels.whatsapp_channel import WhatsAppChannel
+
+logger = logging.getLogger(__name__)
+
+_scheduler: AsyncIOScheduler | None = None
+_whatsapp: "WhatsAppChannel | None" = None
+
+
+def build_scheduler(whatsapp: "WhatsAppChannel") -> AsyncIOScheduler:
+    global _scheduler, _whatsapp
+    _whatsapp = whatsapp
+
+    _scheduler = AsyncIOScheduler(timezone="UTC")
+
+    # WhatsApp-Polling alle 5 Sekunden
+    _scheduler.add_job(
+        _poll_whatsapp,
+        trigger=IntervalTrigger(seconds=5),
+        id="whatsapp-poll",
+        name="WhatsApp incoming messages",
+        max_instances=1,
+        coalesce=True,
+    )
+
+    return _scheduler
+
+
+async def _poll_whatsapp() -> None:
+    if _whatsapp:
+        await _whatsapp.poll_incoming()