- TopologyList header now uses .page-header + .page-title-group +
.page-sub like Dashboard/Attackers/DeckyFleet; title typography and
separator match the rest of the app.
- Pluralisation fix: '0 topologyies' → '0 TOPOLOGIES', singular '1
TOPOLOGY'.
- When the list is empty the EmptyState renders in its own flex
container that fills the viewport so the card is centered both
axes, with bumped icon/title/hint sizing for the hero treatment.
Active/degraded/failed/deploying topologies cannot be deleted
without first transitioning to torn_down, but the UI had no way
to trigger that. Add POST /topologies/{id}/teardown mirroring the
deploy endpoint (background task, 202 Accepted), and a
click-to-arm TEARDOWN button on the topology list card that shows
whenever the row is in a teardown-eligible state.
