Bulk delete: filter IDs through whereCompany() before deleting in all
controllers (Invoices, Payments, Items, Expenses, Estimates, Recurring
Invoices). Previously, any user could delete records from other companies
by providing cross-company IDs.
Transfer ownership: fix inverted hasCompany() check that allowed
transferring company ownership to users who do NOT belong to the company,
while blocking users who DO belong.
Ref #567