feat(admin): archive tabs for business inquiries and reviews

Inquiries: completed and rejected inquiries move to an "Archiv" tab;
resetting the status brings them back. Reviews: new "Ablehnen" action
(Review.rejectedAt) instead of only deleting; the archive shows decided
reviews in two columns, accepted and rejected, and either decision can
be reversed. Pending counters in the sidebar and dashboard exclude
rejected reviews, and the product page tells the author their review was
not published instead of "still being checked".

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

prisma/migrations/20261002010000_review_rejected_at/migration.sql

@@ -0,0 +1,5 @@
+-- Abgelehnte Bewertungen werden nicht mehr geloescht, sondern markiert und
+-- im Archiv unter "Abgelehnt" gefuehrt. null = nicht abgelehnt.
+
+-- AlterTable
+ALTER TABLE "reviews" ADD COLUMN "rejectedAt" TIMESTAMP(3);