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Alle Code-Pläne (14-01..14-05) fertig + getestet (389/389 API, 151/151 web, tsc clean). D-13 Mandanten-Isolation (write ownerTenantId create-only + read OR-filter + getTender 404-guard) im Code bestätigt, Migration nullable ohne Backfill. Einziger offener Punkt: 14-03 Task 4 = Live-EWS-Test an echtem Postfach (human_verification, kein Code-Gap). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>