swarm-ui: shared Hint, ActionRow, Toolbar, EmptyState, ExternalLink and ExpandableCard replace per-page copies

Hint, ActionRow, Toolbar, EmptyState and ExternalLink replace the muted
text, button row, refresh bar, empty line and _blank anchor that each page
restyled under its own class. ExpandableCard (with a loading twin) holds the
builds and recent-runs cards, which had identical head and body CSS. The
create form's raw checkbox becomes CheckboxField. The components page shows
each new piece.

frontend/packages/swarm-ui/src/pages/LinkMatrixAccountForm.css

@@ -13,6 +13,5 @@
   margin-top: 1em;
 }
 .link-matrix-account-result-ok {
-  margin-top: 1em;
-  color: var(--green);
+  margin-block: 1em;
 }