fix: correct response field mappings and add logout button

- SearchResult uses 'data' not 'items', 'total' not 'totalCount'
- ExecutionStats uses 'p99LatencyMs' not 'p99DurationMs'
- TimeseriesBucket uses 'time' not 'timestamp'
- Add user Dropdown with logout action to LayoutShell

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

ui/src/pages/Dashboard/Dashboard.tsx

@@ -33,7 +33,7 @@ export default function Dashboard() {
   const { data: snapshot } = useProcessorSnapshot(selectedId, processorIdx);
 
   const rows: Row[] = useMemo(() =>
-    (searchResult?.items || []).map((e: ExecutionSummary) => ({ ...e, id: e.executionId })),
+    (searchResult?.data || []).map((e: ExecutionSummary) => ({ ...e, id: e.executionId })),
     [searchResult],
   );
 
@@ -89,7 +89,7 @@ export default function Dashboard() {
         <StatCard label="Total Exchanges" value={stats?.totalCount ?? 0} sparkline={sparklineData} />
         <StatCard label="Failed" value={stats?.failedCount ?? 0} accent="error" />
         <StatCard label="Avg Duration" value={`${stats?.avgDurationMs ?? 0}ms`} />
-        <StatCard label="P99 Duration" value={`${stats?.p99DurationMs ?? 0}ms`} accent="warning" />
+        <StatCard label="P99 Duration" value={`${stats?.p99LatencyMs ?? 0}ms`} accent="warning" />
         <StatCard label="Active" value={stats?.activeCount ?? 0} accent="running" />
       </div>