pi-neuralwatt v0.12.0

fbd1b1c: Adopt @aliou/pi-utils-settings 0.19.1 versioned migrations.

Bumps the dependency and adds semver version strings to all config migrations, leaving their content-based shouldRun gates intact. Switches schema generation to pi-settings-schema.
32ba87a: Add an X-NW-Conversation-ID header (set to the active Pi session id) to every Neuralwatt request so the gateway can correlate requests within a session.