Replaces the old "untagged" sentinel tag with a proper per-file workflow
status: needs_review starts true on upload/import and is cleared by an
explicit action (no auto-clear on tagging). Surfaced as a filter token
(r=1 needs review, r=0 done) so it combines with tag/MIME conditions, and
toggled via POST /files/bulk/review (single id or many, edit-ACL enforced,
audit-logged as file_review).
needs_review lives on data.files (column added to the original 003 migration,
partial index in 006, action type seeded in 007).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>