Assets vs liabilities + equity for one fiscal year, signed by natural side.

Window rules as the trial balance (fiscal_year defaults to the latest posted year; no all-years mode, ZET-155). With period_id this is a movements aggregate over that period, not a position.

⚠️ Balances as assets == liabilities_and_equity, NOT liabilities + equity: the GL has no P&L→equity closing entry, so equity is the equity accounts alone and net_result is folded into liabilities_and_equity. It is a position only for a year whose book carries its opening batch; otherwise it is that year's movements and equity is empty.

Cut by the stamped fiscal_year_id, not posting date (fiscal_year_cut, ZET-166).