- Add onAiAutoPlace prop and handleAiAutoPlaceClick with aiLoading state to PreparePanel
- Add violet AI Auto-place button above Preview button (Draft documents only)
- Add aiPlacementKey state and handleAiAutoPlace callback in DocumentPageClient
- handleAiAutoPlace: POST /api/documents/[id]/ai-prepare, merges textFillData, increments aiPlacementKey, resets previewToken
- Pass aiPlacementKey to PdfViewerWrapper and onAiAutoPlace to PreparePanel