Each year's ouverture (opening balance) should match the previous
year's calculated closing balance (that year's own ouverture + every
movement dated within it). The historical spreadsheets carry real
gaps here that were preserved as-is during migration -- this surfaces
them per compte, on the ouverture row(s) they affect, the same way
the per-ligne écart column already does, rather than correcting them.
New LedgerStatsController::reconciliationOuverture() endpoint (a
single grouped SQL aggregate over ouverture vs. non-ouverture lines
per year/compte, not per-node loading) backs a small badge shown only
on the affected ouverture row(s), scoped to whichever compte that
specific row's répartition touches.