Implement BaseModel class, TimestampMixin, TzDateTime type; cleanup Task model

tofu_api/common/database/typing.py

@@ -0,0 +1,14 @@
+from typing import TypeVar, Union
+
+from sqlalchemy import Column
+from sqlalchemy.orm import RelationshipProperty
+
+__all__ = [
+    'Col',
+    'Rel',
+]
+
+# Define type aliases for SQLAlchemy columns and relationships in declarative models
+_T = TypeVar('_T')
+Col = Union[Column, _T]
+Rel = Union[RelationshipProperty, _T]