v3 port of the v2 authorization fixes.
- Notes IDOR (GHSA-85wc): NotePolicy checks the note's company_id and
NotesController passes the bound model to authorize() on show/update/destroy.
- Estimate<->Invoice convert IDOR (GHSA-j2vg): EstimatesController::convertToInvoice
and InvoicesController::convertToEstimate authorize 'view' on the source
document before creating the target.
- Member bulk-delete (GHSA-wxrv): MembersController scopes ids via
User::whereCompany() before MemberService::delete.
Adds feature tests for cross-company 403s + same-company happy paths.