Add configuration rules, refactor settings management, and enhance import functionality

- Introduced a new configuration file `.cursorrules` to define coding standards, error handling, testing requirements, and project-specific guidelines.
- Refactored `config.py` to implement a `Settings` dataclass for better management of environment variables, improving testability and maintainability.
- Updated the import duty schedule handler to utilize session management with `session_scope`, ensuring proper database session handling.
- Enhanced the import service to streamline the duty schedule import process, improving code organization and readability.
- Added new service layer functions to encapsulate business logic related to group duty pinning and duty schedule imports.
- Updated README documentation to reflect the new configuration structure and improved import functionality.

db/__init__.py

@@ -2,13 +2,14 @@
 
 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.session import get_engine, get_session_factory, get_session, session_scope
 from db.repository import (
     delete_duties_in_range,
     get_or_create_user,
     get_or_create_user_by_full_name,
     get_duties,
     insert_duty,
+    set_user_phone,
 )
 
 __all__ = [
@@ -23,11 +24,13 @@ __all__ = [
     "get_engine",
     "get_session_factory",
     "get_session",
+    "session_scope",
     "delete_duties_in_range",
     "get_or_create_user",
     "get_or_create_user_by_full_name",
     "get_duties",
     "insert_duty",
+    "set_user_phone",
     "init_db",
 ]