Initial commit: Kalendartool (Next.js, Prisma, Docker)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

prisma/migrations/20261001000000_user_hub_id/migration.sql

@@ -0,0 +1,5 @@
+-- Fügt die hub_id-Spalte hinzu: stabile User-ID der MultiToolApp-Plattform.
+-- null = rein lokaler Account; unique verhindert doppelte Kopplung.
+
+ALTER TABLE "users" ADD COLUMN "hub_id" TEXT;
+CREATE UNIQUE INDEX "users_hub_id_key" ON "users"("hub_id");