Delete an empty, unsealed fiscal year and its scaffolding (accountant).

ZCT-510, approved by the owner ruling of 2026-09-03 alongside the refusal that stops such years being opened by accident. Coding one document could open a whole fiscal year as a side effect, and until this route existed nothing on the fiscal-year surface could remove the result — the residue simply stayed in the company's calendar and in every year picker.

Refused unless the year has zero journal entries and is not sealed, and that gate is what keeps Swiss retention rules out of scope: a year carrying any posting is untouchable. Deleting also refuses on any other FY-scoped bookkeeping record (period balances, provisions, dividend resolutions, fixed-asset activations, journal lines whose account belongs to the year), naming which one blocked. The year's seal/unseal history does not block (ZCT-807): a year that was sealed and then unsealed is deletable once it is empty, and that history is kept rather than deleted with it.

What it removes with the year is only what serves the year: its chart of accounts, its VAT/opening-balance settings, its periods and its sequence counters. 404 for an unknown or cross-tenant year; 409 for every refusal above.

MsgResponse, not 204, because that is what both sibling DELETE routes in this file answer (delete_gl_account, delete_gl_journal_entry) and it is the dominant convention across the api shell — the four 204 routes are the exception.