fix: all lint errors, test + lint pre-commit passing

Frontend:
- Split nodeTypes/edgeTypes into separate .ts files (react-refresh)
- Remove setState-in-effect in NodeModal (key prop reset)
- Fix handleSave accessed before declaration (useRef pattern)
- Exclude src/components/ui/** from eslint (shadcn generated)
- Use defineConfig from vitest/config for test type support

Backend:
- ruff --fix: sort imports, datetime.UTC alias
- Raise line-length to 120, ignore E501 in tests
- Break long update_node/update_edge signatures
- pyproject.toml: per-file-ignores for tests

backend/app/db/models.py

@@ -1,14 +1,14 @@
 import uuid
-from datetime import datetime, timezone
+from datetime import UTC, datetime
 
-from sqlalchemy import JSON, Boolean, DateTime, Float, ForeignKey, Integer, String, Text
+from sqlalchemy import JSON, DateTime, Float, ForeignKey, Integer, String, Text
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
 from app.db.database import Base
 
 
 def _now() -> datetime:
-    return datetime.now(timezone.utc)
+    return datetime.now(UTC)
 
 
 def _uuid() -> str: