Write a SpacetimeDB backend module in C# that defines one table and two reducers for client lifecycle events.

TABLE
- Event
  - Struct: Event
  - Fields:
    - Id: int (primary key, auto-increment)
    - Kind: string

REDUCERS
- ClientConnected: when a client connects, insert exactly one row into Event with Kind="connected"
- ClientDisconnected: when a client disconnects, insert exactly one row into Event with Kind="disconnected"
