﻿Write a SpacetimeDB backend module in Rust that defines two tables and a reducer that looks up a row by primary-key index and writes a projection to another table.

TABLES
- user
  - Struct: User
  - Fields:
    - id: i32 (primary key)
    - name: String
    - age: i32
    - active: bool

- result
  - Struct: ResultRow
  - Fields:
    - id: i32 (primary key)
    - name: String

REDUCERS
- lookup_user_name: given id:i32, find the user row with that id using the index and insert (id, name) into result.
