Write a SpacetimeDB backend module in TypeScript that demonstrates sum types (enums) used in tables.

TYPES
- Rect
  - width: number (i32)
  - height: number (i32)
- Shape (sum type / enum)
  - circle: number (i32 radius)
  - rectangle: Rect

TABLE
- result
  - Fields:
    - id: number (i32, primary key)
    - value: Shape

REDUCERS
- setCircle: given id:number, radius:number, insert row with value=Shape.circle(radius)
