DR-042 — Compute posture: pipeline on-prem, app on Vercel; on-prem = residence + processing

The split stays: the pipeline lives on-prem (data-adjacent, compute-heavy, single-tenant); the Next.js app stays on Vercel (stateless, public-by-design, no client data at rest — the tenant boundary is the Supabase project). App-on-VPS is a per-client contractual option, not the default.