A user importing invoices from Visma hit INVOICE_SEND_PAYMENT_ACCOUNT_MISSING
on mark-sent and could not find where to add the account: the message said
"under Fakturering" without saying it lives in settings. Spell out the full
path (Installningar -> Fakturering) in the Swedish and English messages and
the remediation line, matching the wording other structured errors already use.
Copy-only: error code, status, and behavior unchanged.
Claude-Session: https://claude.ai/code/session_01Vh2e8MkbnTbTwRDDLV3tTo
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>