feat: add unified linting scripts and git hooks for code quality enforcement

- Introduced `lint` and `lint-fix` applications in `flake.nix` for unified linting of backend (Python) and frontend (TypeScript/Svelte) code.
- Added `scripts/lint.sh` for manual linting execution.
- Created `scripts/install-hooks.sh` to set up git hooks for automatic linting before commits and optional tests before pushes.
- Updated `README.md` with instructions for using the new linting features and git hooks.

backend/app/database/models/board_image.py

@@ -1,6 +1,8 @@
 """BoardImage junction model."""
+
 import uuid
 from datetime import datetime
+
 from sqlalchemy import Column, DateTime, ForeignKey, Integer, UniqueConstraint
 from sqlalchemy.dialects.postgresql import JSONB, UUID
 from sqlalchemy.orm import relationship
@@ -26,17 +28,15 @@ class BoardImage(Base):
             "opacity": 1.0,
             "flipped_h": False,
             "flipped_v": False,
-            "greyscale": False
-        }
+            "greyscale": False,
+        },
     )
     z_order = Column(Integer, nullable=False, default=0, index=True)
     group_id = Column(UUID(as_uuid=True), ForeignKey("groups.id", ondelete="SET NULL"), nullable=True, index=True)
     created_at = Column(DateTime, nullable=False, default=datetime.utcnow)
     updated_at = Column(DateTime, nullable=False, default=datetime.utcnow, onupdate=datetime.utcnow)
 
-    __table_args__ = (
-        UniqueConstraint("board_id", "image_id", name="uq_board_image"),
-    )
+    __table_args__ = (UniqueConstraint("board_id", "image_id", name="uq_board_image"),)
 
     # Relationships
     board = relationship("Board", back_populates="board_images")
@@ -45,4 +45,3 @@ class BoardImage(Base):
 
     def __repr__(self) -> str:
         return f"<BoardImage(board_id={self.board_id}, image_id={self.image_id})>"
-