Get Balance

Net position across unsettled splits, from the caller's side.

Derived from the rows on every request rather than stored, so it cannot drift from them: adding, settling or editing a split changes the answer immediately and there is no second copy to keep in step.

Settled rows are excluded — settling means "we have squared this up between us", so a settled split is no longer outstanding. Rows with no recorded payer are excluded too and counted in needs_payer.