feat: DataTable scrollable layout with 200+ mock exchanges

Make Dashboard table fill viewport height with sticky header/footer
and internal scrolling. Expand mock exchange data from 15 to 200
records and Inventory showcase from 5 to 500 records.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/pages/Dashboard/Dashboard.tsx

@@ -425,6 +425,7 @@ export function Dashboard() {
             selectedId={selectedId}
             sortable
             flush
+            fillHeight
             rowAccent={handleRowAccent}
             expandedContent={(row) =>
               row.errorMessage ? (