GET /api/wahl/guest/overview (guest JWT) returns the open Wahlen for the
guest's KC, each with its workshops and the guest's own current priorities
(null if not yet submitted) — everything the client needs to render the
Wahl form without any LT-only endpoint. Verified end to end against a local
Postgres (guest login -> overview -> submit -> re-fetch).
prisma/seed-dev.js: minimal dev fixture (one KC "DEV123" + Gemeinde + open
Wahl with three workshops).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>