fix: side-by-side layout for treemap and punchcard heatmaps

Treemap on left (3fr), two punchcards stacked on right (2fr) using
new .vizRow grid layout. Replaces full-width stacked arrangement.

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

ui/src/pages/DashboardTab/DashboardTab.module.css

@@ -123,6 +123,19 @@
   width: 100%;
 }
 
+/* Visualization row: treemap left (wider) + punchcards right (stacked) */
+.vizRow {
+  display: grid;
+  grid-template-columns: 3fr 2fr;
+  gap: 16px;
+}
+
+.punchcardStack {
+  display: flex;
+  flex-direction: column;
+  gap: 16px;
+}
+
 /* Errors section */
 .errorsSection {
   background: var(--bg-surface);