Add a “Send invoice email” option to the custom void/regenerate flow, enabled by default.

When disabled, Lago should not send the invoice.finalized notification email for the regenerated invoice. This suppression should apply only to that specific operation, including invoices finalized asynchronously through a tax provider.

Currently, the only workaround is to temporarily disable invoice.finalized emails at the billing-entity level, which can unintentionally suppress notifications for other invoices finalized during the same period. Existing behavior should remain unchanged when the option is enabled or omitted.