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/components/LayoutShell.tsx

@@ -1,5 +1,5 @@
 import { Outlet, useNavigate, useLocation } from 'react-router';
-import { AppShell, Sidebar, TopBar, CommandPalette, CommandPaletteProvider, GlobalFilterProvider, useCommandPalette } from '@cameleer/design-system';
+import { AppShell, Sidebar, TopBar, CommandPalette, CommandPaletteProvider, GlobalFilterProvider, useCommandPalette, Dropdown, Avatar } from '@cameleer/design-system';
 import { useRouteCatalog } from '../api/queries/catalog';
 import { useAuthStore } from '../auth/auth-store';
 import { useMemo, useCallback } from 'react';
@@ -9,7 +9,7 @@ function LayoutContent() {
   const navigate = useNavigate();
   const location = useLocation();
   const { data: catalog } = useRouteCatalog();
-  const { username, roles } = useAuthStore();
+  const { username, roles, logout } = useAuthStore();
   const { open: paletteOpen, setOpen: setPaletteOpen } = useCommandPalette();
 
   const sidebarApps: SidebarApp[] = useMemo(() => {
@@ -56,10 +56,22 @@ function LayoutContent() {
         />
       }
     >
-      <TopBar
-        breadcrumb={breadcrumb}
-        user={username ? { name: username } : undefined}
-      />
+      <div style={{ display: 'flex', alignItems: 'center' }}>
+        <TopBar
+          breadcrumb={breadcrumb}
+          user={username ? { name: username } : undefined}
+        />
+        {username && (
+          <Dropdown
+            trigger={<Avatar name={username} size="sm" />}
+            items={[
+              { label: `Signed in as ${username}`, disabled: true },
+              { divider: true, label: '' },
+              { label: 'Logout', onClick: () => { logout(); navigate('/login'); } },
+            ]}
+          />
+        )}
+      </div>
       <CommandPalette
         open={paletteOpen}
         onClose={() => setPaletteOpen(false)}