Report detail pages now link to the underlying POs, addressing the PR #126
review comment: drilling into a cost centre or accounting code opens PO
History pre-filtered to that dimension and the period in view.
- Cost Centre / Accounting Code detail pages gain a "View POs" link.
- periodRange() maps the on-screen period onto History's approved-date
window (weekly→month, monthly→FY, yearly→full span); spend is dated by
approvedAt.
- PO History gains an accountId filter (any tree node, expanded to leaves
via accountLeafIds()) matching PO-level OR line-item accounts — the same
basis the reports use.
- History page + CSV/PDF export share one buildPoHistoryWhere() builder so
they never diverge.
- Tests: unit (periodRange, accountLeafIds) + integration (History account
filter across PO-level/line-item, with the approved window).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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