Enhance Telegram bot with database integration and API features

- Added SQLite database support with Alembic for migrations.
- Implemented FastAPI for HTTP API to manage duties.
- Updated configuration to include database URL and HTTP port.
- Created entrypoint script for Docker to handle migrations and permissions.
- Expanded command handlers to register users and display duties.
- Developed a web application for calendar display of duties.
- Included necessary Pydantic schemas and SQLAlchemy models for data handling.
- Updated requirements.txt to include new dependencies for FastAPI and SQLAlchemy.

config.py

@@ -1,5 +1,6 @@
 """Load configuration from environment. Fail fast if BOT_TOKEN is missing."""
 import os
+from pathlib import Path
 
 from dotenv import load_dotenv
 
@@ -8,3 +9,8 @@ load_dotenv()
 BOT_TOKEN = os.getenv("BOT_TOKEN")
 if not BOT_TOKEN:
     raise SystemExit("BOT_TOKEN is not set. Copy .env.example to .env and set your token from @BotFather.")
+
+DATABASE_URL = os.getenv("DATABASE_URL", "sqlite:///data/duty_teller.db")
+MINI_APP_BASE_URL = os.getenv("MINI_APP_BASE_URL", "").rstrip("/")
+HTTP_PORT = int(os.getenv("HTTP_PORT", "8080"))
+DATA_DIR = Path(__file__).resolve().parent / "data"