Write a SpacetimeDB backend module in Rust that defines a task table and a result table, with a reducer that finds the first incomplete task and writes it to the result table.

TABLES
- task
  - Struct: Task
  - Fields:
    - id: u64 (primary key, auto_inc)
    - title: String
    - completed: bool

- first_incomplete
  - Struct: FirstIncomplete
  - Fields:
    - task_id: u64 (primary key)
    - title: String

REDUCERS
- find_first_incomplete(ctx)
  - Iterate through the task table
  - Find the first task where completed is false
  - If found, insert it into first_incomplete
