Add pyproject.toml for consolidated project configuration and replace Black, isort, and Flake8 with Ruff

- Introduced `pyproject.toml` to centralize backend tool configurations (e.g., Ruff, mypy, coverage, pytest).
- Replaced Black, isort, and Flake8 with Ruff for linting, formatting, and import sorting.
- Updated `requirements.txt` to include Ruff and remove replaced tools.
- Added `Makefile` to streamline development workflows with commands for linting, formatting, type-checking, testing, and cleanup.

backend/app/models/__init__.py

@@ -2,17 +2,25 @@
 Models package initialization.
 Imports all models to ensure they're registered with SQLAlchemy.
 """
+
 # First import Base to avoid circular imports
 from app.core.database import Base
+
 from .base import TimestampMixin, UUIDMixin
 from .organization import Organization
+
 # Import models
 from .user import User
-from .user_organization import UserOrganization, OrganizationRole
+from .user_organization import OrganizationRole, UserOrganization
 from .user_session import UserSession
 
 __all__ = [
-    'Base', 'TimestampMixin', 'UUIDMixin',
-    'User', 'UserSession',
-    'Organization', 'UserOrganization', 'OrganizationRole',
-]
+    "Base",
+    "Organization",
+    "OrganizationRole",
+    "TimestampMixin",
+    "UUIDMixin",
+    "User",
+    "UserOrganization",
+    "UserSession",
+]