Onboarding Setup

First-run setup: create the user's channel + style from a YouTube link or a preset, then kick off ONE free style analysis for the YouTube path.

This runs BEFORE the paywall. A brand-new user is inactive with zero credits, so the analysis is queued billing-bypassed (charge_credits=False — the same path BYOK uses) and we eat its few-cent cost. Channel creation is allowed for inactive users by the loosened limit trigger (migration 0146); everything else (generation) stays gated behind an active plan.

Idempotent for resume/retry: reuses the user's existing onboarding channel (the free plan caps them at one) and only re-queues analysis when the style hasn't been analysed yet.

An ACTIVE subscriber can run it too (the /app/onboarding?preview=1 walk- through): they get a fresh channel and a normally-billed analysis — exactly what the /styles flow would charge — so nothing here is free for a paying account, and the resume logic (which assumes the single free-plan channel) is skipped for them.