Webhook /webhook/onboard → read Clients → compute next C-#### →
append Clients row (status onboarding, renewal_date auto from billing
cycle) → seed Projects row (checklist from services, +14d go-live) →
log Activity → Telegram confirmation. Sheets writes retry on fail.
Verified end-to-end (C-0002 created across all three tabs).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
