Add `child()` method to ILogger interface

[AdamBHolt]

Priority: MED
Package: @saga-ed/soa-logger
Coach ref: hipponot/nimbee#8035

The ILogger interface has no child() method. Per-request loggers with bound context (e.g., requestId) cannot be created. All downstream service/data layer logs lack request correlation.

Requested changes:

1. Add child(bindings: Record<string, unknown>): ILogger to the ILogger interface
2. Implement in PinoLogger (Pino natively supports logger.child())

Combined with AsyncLocalStorage, this enables automatic request correlation across the entire call stack without threading logger instances manually.