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.

config.py

@@ -0,0 +1,43 @@
+from functools import lru_cache
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    model_config = SettingsConfigDict(env_file=".env", env_file_encoding="utf-8", extra="ignore")
+
+    # API
+    api_key: str = "changeme-secret-key"
+    host: str = "0.0.0.0"
+    port: int = 8000
+    debug: bool = False
+
+    # Telegram
+    telegram_token: str = ""
+
+    # WhatsApp (Green API)
+    whatsapp_id_instance: str = ""
+    whatsapp_api_token: str = ""
+
+    # SMS / USB-Modem
+    sms_port: str = "/dev/ttyUSB0"
+    sms_baud_rate: int = 115200
+    sms_enabled: bool = False
+
+    # Datenbank
+    database_url: str = "sqlite:///./mcm.db"
+
+    @property
+    def telegram_enabled(self) -> bool:
+        return bool(self.telegram_token)
+
+    @property
+    def whatsapp_enabled(self) -> bool:
+        return bool(self.whatsapp_id_instance and self.whatsapp_api_token)
+
+
+@lru_cache
+def get_settings() -> Settings:
+    return Settings()
+
+
+settings = get_settings()