US payment NACHA – Addenda Extension

Adds 05 Addenda records and correct Entry/Addenda counts to Odoo's l10n_us_payment_nacha. This lightweight extension enhances Odoo's native NACHA ACH export by emitting a single 05 Addenda record per payment (when a memo is present), setting the Addenda Record Indicator, and fixing the Entry/Addenda Count in Batch (record 8) and File (record 9) control records. No new menus or models - just compliant output, out of the box.