StepUpload now has 3 phases: 1. File selection: drop zone / file picker → shows preview 2. Review: title input, category, file info → "Hochladen" button 3. Uploaded: shows session image → "Weiter" button No more auto-advance after upload. User controls every step. openSession() removed from onUploaded callback to prevent step-reset race condition. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>