Retained valuation migration evidence and audit

See the repository retirement boundary.

Valuation migration dates, periods, final proposals, statuses, decisions, explanations, and logs remain in their original fields. The valuation-only legacy manual-period selector is immutable. The shared history mixin protects all retained evidence, including imports and superuser writes.

Fiscal Migration Audit, finding drilldowns, the overview, and read-only history views retain their XML IDs and Accounting Manager/company restrictions. The baseline model and fingerprint reader remain in pmis_account_dates. Missing evidence cannot be recreated by running an audit.

Layer conversion, retry, acceptance, explanation editing, historical holds, the transient review-note wizard, old upgrade scripts, and their obsolete tests have been removed. Since 18.0.2.0.2, the retained conversion job is inactive and inert, including upgrades of existing noupdate records. Normal accounting recognition changes no longer rewrite historical decisions. Current valuation dates still follow accounting, stock, or creation chronology through the permanent implementation.

Keep the shared audit overview model, permanent audit menus, valuation-date correction form/action, and permanent manager valuation-read permission. This cleanup removes no durable evidence columns, records, fingerprints, or company-access rules.