refactor: unify all brand icons to single SVG from DS v0.1.36

Replace PNG favicons and brand logos with cameleer3-logo.svg from
@cameleer/design-system/assets. Favicon, login dialog, and sidebar
all use the same SVG. Remove PNG favicon files from public/.

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

ui/src/components/LayoutShell.tsx

@@ -16,7 +16,7 @@ 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 sidebarLogo from '@cameleer/design-system/assets/cameleer3-logo.svg';
 import { Box, Settings, FileText, ChevronRight, Square, Pause, Star, X } from 'lucide-react';
 import { useQueryClient } from '@tanstack/react-query';
 import { useRouteCatalog } from '../api/queries/catalog';