Backend: restructured /vertical/:code/metrics endpoint to return metrics
with nested sub_teams arrays. Each metric now has the ALL: rollup as the
primary row and individual team breakdowns (ACCESS-OPS, STEAM, etc.) as
sub_teams. Also returns a teams array for the filter UI.
Frontend: VerticalDetailView now supports two interaction modes:
- Expand/collapse: click the arrow on any metric row to reveal sub-team
breakdown inline (teal-highlighted rows beneath the parent)
- Team filter: click a team button to filter the entire table to show
only that team's numbers per metric
Both modes avoid double-counting by using the ALL: rollup for totals
and only showing sub-team data as supplementary detail.
