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.module.css

@@ -4,7 +4,10 @@
   overflow-y: auto;
   padding: 20px 24px 40px;
   min-width: 0;
+  min-height: 0;
   background: var(--bg-body);
+  display: flex;
+  flex-direction: column;
 }
 
 /* Filter bar spacing */
@@ -19,6 +22,10 @@
   border-radius: var(--radius-lg);
   box-shadow: var(--shadow-card);
   overflow: hidden;
+  flex: 1;
+  min-height: 0;
+  display: flex;
+  flex-direction: column;
 }
 
 .tableHeader {