fix: revert to public/ brand assets — DS exports field blocks imports

The @cameleer/design-system package.json exports field doesn't include
assets/, causing production build failures. Copy PNGs to public/ and
reference via basePath until DS adds asset exports.

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

ui/src/components/LayoutShell.tsx

@@ -16,7 +16,6 @@ import {
   useStarred,
 } from '@cameleer/design-system';
 import type { SearchResult, SidebarTreeNode } from '@cameleer/design-system';
-import sidebarLogo from '@cameleer/design-system/assets/cameleer3-48.png';
 import { Box, Settings, FileText, ChevronRight, Square, Pause, Star, X } from 'lucide-react';
 import { useQueryClient } from '@tanstack/react-query';
 import { useRouteCatalog } from '../api/queries/catalog';
@@ -626,7 +625,7 @@ function LayoutContent() {
 
   // --- Render -------------------------------------------------------
   const camelLogo = (
-    <img src={sidebarLogo} alt="" style={{ width: 28, height: 28 }} />
+    <img src={`${config.basePath}cameleer3-logo-48.png`} alt="" style={{ width: 28, height: 28 }} />
   );
 
   const sidebarElement = (