Update Company Settings Route

Finance -> Company settings: save edits to Pigeonly's billing identity -- company name, the invoice/remittance mailing address, remittance payee/address/instructions, bank name, ACH routing and account numbers, the invoice contact email and mailing instructions.

GATED ON finance:write, the Finance section's existing write key (held by the Finance role and by Frederick), for everything EXCEPT the bank.

⛔THE BANK IS FREDERICK'S ALONE. Frederick, 2026-09-24: "Nobody can change bank details except me." A save that touches a bank field needs finance:bank:write as well -- checked in the service (company_settings.update_company_settings) against the REAL signed-in person, so viewing as Frederick does not lend his key. Refused with 403 and nothing written. Every bank change that does go through DMs Frederick (send_bank_change_alarm); the response's bank_alarm says whether it reached him.

Every changed field is audited (company_settings_changes: who, when, which field, old/new -- bank numbers as last four). A bad routing or account number refuses the whole save with 422 and writes nothing.