Adds the multiEntryOrdering jsonb column + interactive order picker: the
largest-count multi-entry sample is shown with a building-part dropdown per
file position (one Main building + Extensions), validated as a permutation.
A PATCH route persists { count: permutation } + confirmed, and Finalise is
disabled until the ordering is confirmed when the upload is multi-entry.
Migration for the new column is intentionally not included here — generated
after origin/main is merged (its multi_entry_summary migration lands first).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
