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.

db/__init__.py

@@ -0,0 +1,11 @@
+"""Database layer: SQLAlchemy models, Pydantic schemas, repository, init."""
+from db.models import Base, User, Duty
+from db.schemas import UserCreate, UserInDb, DutyCreate, DutyInDb, DutyWithUser
+from db.session import get_engine, get_session_factory, get_session
+from db.repository import get_or_create_user, get_duties, insert_duty
+
+
+def init_db(database_url: str) -> None:
+    """Create tables from metadata (Alembic migrations handle schema in production)."""
+    engine = get_engine(database_url)
+    Base.metadata.create_all(bind=engine)