Drop legacy document columns and approver tables

The title, classification, and document_type columns have been moved to
document_versions. The document_approvers and document_version_approvers
tables have been replaced by approval quorums and decisions.

Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>

pkg/coredata/migrations/20260331T120000Z.sql

@@ -8,5 +8,4 @@ WHERE dv.document_id = d.id;
 
 ALTER TABLE document_versions ALTER COLUMN document_type DROP DEFAULT;
 
--- TODO: drop the document_type column from documents.
 ALTER TABLE documents ALTER COLUMN document_type SET DEFAULT 'OTHER';