feat(branding): white-label — public /branding, admin write, shell theming (#41)

app_settings branding.* keys (product name, logo/favicon URLs, accent
color, docs/support links). Public GET /branding so login and shell
theme pre-auth; admin writes via PUT /settings.

useBranding() applies document.title, accent CSS var and favicon;
BrandWordmark replaces hardcoded wordmarks; admin Platform settings
gain a Branding form. MCP containr_branding_get + settings_update.

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Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/frontend/src/app/layout/PlatformShell.tsx

@@ -41,7 +41,7 @@ import {
 import { signOutAuthSession } from '@/lib/auth-client';
 import { isDemoSearch } from '@/lib/demo-mode';
 import { useAuthSession } from '@/lib/use-auth-session';
-import { BannerBar, useToast } from '@/shared/components';
+import { BannerBar, BrandWordmark, useToast } from '@/shared/components';
 
 type NavItem = { label: string; href: string; icon: typeof FolderKanban; hint: string };
 type NavSection = { title: string; items: NavItem[] };
@@ -398,7 +398,7 @@ export function PlatformShell() {
             }}
           >
             <NavLink to={href('/projects')} className="mr-5 text-sm font-extrabold tracking-tight text-[var(--text-primary)]" style={{ fontFamily: 'Inter, sans-serif' }}>
-              contain<span style={{ color: 'var(--accent-primary)' }}>r</span>
+              <BrandWordmark />
             </NavLink>
 
             <div className="flex items-center gap-5">