RED phase (TDD) for UI-03/04 per-user triage (gelesen/ungelesen, Favorit).
Adds the TenderTriage Prisma model (userId-scoped, onDelete: Cascade to
Tender per Pitfall 6) and its migration, plus a failing spec proving
upsert idempotency, strict userId scoping (V4/IDOR, T-11-10), and cascade
consistency — service implementation follows in the GREEN commit.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
