Fills the plan's known gap where Gemeinde existed only as a Prisma model.
GemeindeModule exposes Leitungsteam-only create/list/get/update/delete
under /api/gemeinde, each mutation captured into the sync log like the
other feature services. Unique-name-per-KC violations surface as 409.
Docs (plan + backend README) updated to drop the gap and next-step item.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
