feat: set browser tab title and favicon from customer branding

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

packages/admin/src/routes/__root.tsx

@@ -1,11 +1,29 @@
 import { createRootRoute, Outlet } from '@tanstack/react-router'
 import { Toaster } from 'sonner'
+import { useEffect } from 'react'
 
 export const Route = createRootRoute({
   component: RootLayout,
 })
 
 function RootLayout() {
+  useEffect(() => {
+    fetch('/v1/store/branding')
+      .then((r) => r.ok ? r.json() : null)
+      .then((data: { name: string | null; hasLogo: boolean } | null) => {
+        if (!data) return
+        if (data.name) document.title = data.name
+        if (data.hasLogo) {
+          const link = document.querySelector<HTMLLinkElement>('link[rel="icon"]')
+            ?? document.createElement('link')
+          link.rel = 'icon'
+          link.href = '/v1/store/logo'
+          document.head.appendChild(link)
+        }
+      })
+      .catch(() => {})
+  }, [])
+
   return (
     <>
       <Outlet />