fix: improve duration formatting (Xm Ys) and truncate exchange IDs

- formatDuration and formatDurationShort now show Xm Ys for durations >= 60s (e.g. "5m 21s" instead of "321s") and 1 decimal for 1-60s range ("6.7s" instead of "6.70s")
- Exchange ID column shows last 8 chars with ellipsis prefix; full ID on hover, copies to clipboard on click

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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

@@ -37,13 +37,8 @@
   text-decoration: underline;
 }
 
-/* Diagram container */
-.diagramSection {
-  background: var(--bg-surface);
-  border: 1px solid var(--border-subtle);
-  border-radius: var(--radius-lg);
-  box-shadow: var(--shadow-card);
-  overflow: hidden;
+/* Diagram container — height override; card styling via tableStyles.tableSection */
+.diagramHeight {
   height: 280px;
 }
 
@@ -90,11 +85,4 @@
   font-weight: 600;
 }
 
-/* Errors section */
-.errorsSection {
-  background: var(--bg-surface);
-  border: 1px solid var(--border-subtle);
-  border-radius: var(--radius-lg);
-  box-shadow: var(--shadow-card);
-  overflow: hidden;
-}
+/* errorsSection removed — use tableStyles.tableSection instead */