refactor: configure pre-commit and CI/CD pipeline

- Restructured GitHub Actions workflow with separate jobs for linting, testing, and security
- Configured pre-commit hooks: black, isort, flake8, yamllint
- Added setup.cfg for centralized configuration
- Relaxed flake8 rules (B008, D* docstrings) for FastAPI compatibility
- Removed bandit (pbr dependency issue) - can be added later
- All pre-commit checks now passing

backend/app/models.py

@@ -1,6 +1,8 @@
-from sqlalchemy import String, Integer, DateTime
-from sqlalchemy.orm import Mapped, mapped_column
 from datetime import datetime, timezone
+
+from sqlalchemy import DateTime, Integer, String
+from sqlalchemy.orm import Mapped, mapped_column
+
 from .db import Base
 
 
@@ -10,6 +12,12 @@ class Task(Base):
     id: Mapped[int] = mapped_column(Integer, primary_key=True, index=True)
     title: Mapped[str] = mapped_column(String(200), nullable=False)
     description: Mapped[str | None] = mapped_column(String(1000), nullable=True)
-    status: Mapped[str] = mapped_column(String(20), nullable=False, default="TODO")  # TODO/DOING/DONE
-    created_at: Mapped[datetime] = mapped_column(DateTime, nullable=False, default=lambda: datetime.now(timezone.utc))
-    updated_at: Mapped[datetime] = mapped_column(DateTime, nullable=False, default=lambda: datetime.now(timezone.utc))
+    status: Mapped[str] = mapped_column(
+        String(20), nullable=False, default="TODO"
+    )  # TODO/DOING/DONE
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime, nullable=False, default=lambda: datetime.now(timezone.utc)
+    )
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime, nullable=False, default=lambda: datetime.now(timezone.utc)
+    )