feat: upgrade design system to v0.1.19, use onNavigate/fillHeight, add SonarQube workflow

- Use Sidebar onNavigate callback instead of display:contents click interception
- Use DataTable fillHeight prop instead of manual scroll wrapper divs
- Fix DataTable scroll/pagination by adding overflow:hidden to content container
- Fix left panel in split view to use flex column instead of overflow:auto
- Make error tab stack trace scrollable for large traces
- Add nightly SonarQube workflow with manual trigger support

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

ui/src/pages/Dashboard/Dashboard.module.css

@@ -5,25 +5,8 @@
   flex: 1;
   min-height: 0;
   min-width: 0;
-  background: var(--bg-body);
-}
-
-/* Table section — stretches to fill and scrolls internally */
-
-
-.tableSection {
-  display: flex;
-  flex-direction: column;
-  flex: 1;
-  min-height: 0;
-  background: var(--bg-surface);
   overflow: hidden;
-}
-
-.tableScroll {
-  flex: 1;
-  min-height: 0;
-  overflow-y: auto;
+  background: var(--bg-body);
 }
 
 .tableHeader {