- Replace legacy Optional imports with modern str | None syntax
- Type JSONB columns as Mapped[list[dict[str, Any]]]
- Escape SQL LIKE wildcards (%, _) in diagram search
- Type DiagramNode.position as Position(x, y) Pydantic model
- Wrap AI response parsing in KeyError handler for clean 422 errors
- Remove unused Optional/TYPE_CHECKING imports from schemas/models
- Extract _get_available_slugs helper to DRY duplicate queries
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
