Write a SpacetimeDB backend module in C# that defines a scheduled table and seeds one schedule entry.

TABLE
- TickTimer
  - Struct: TickTimer
  - Fields:
    - ScheduledId: ulong (primary key, auto-increment)
    - ScheduledAt: ScheduleAt
  - Scheduling:
    - Reducer: Tick
    - Column: ScheduledAt

REDUCERS
- Tick: scheduled reducer that accepts the scheduled row
- Init: insert exactly one row into TickTimer that schedules a repeating interval of 50_000 microseconds
