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.

Generated with [Devin](https://devin.ai)

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

app/frontend/src/shared/components/BrandWordmark.tsx

@@ -0,0 +1,28 @@
+import { useBranding } from '@/lib/use-branding';
+
+/**
+ * Instance wordmark — renders the configured logo when set, otherwise the
+ * product name with the signature accent on the last character
+ * ("contain[r]"). Falls back to Containr branding.
+ */
+export function BrandWordmark({ className = '' }: { className?: string }) {
+  const branding = useBranding();
+
+  if (branding.logoUrl) {
+    return (
+      <img
+        src={branding.logoUrl}
+        alt={branding.productName}
+        className={`h-6 w-auto object-contain ${className}`}
+      />
+    );
+  }
+
+  const name = branding.productName;
+  return (
+    <span className={className}>
+      {name.slice(0, -1)}
+      <span style={{ color: 'var(--accent-primary)' }}>{name.slice(-1)}</span>
+    </span>
+  );
+}

app/frontend/src/shared/components/index.ts

@@ -10,3 +10,4 @@ export * from './CommandPalette';
 export * from './StatusBadge';
 export { useToast } from '../hooks/use-toast';
 export type { ToastType, ToastContextValue } from '../hooks/use-toast';
+export * from './BrandWordmark';