React 19 modernization: forwardRef removal, Compiler, ErrorBoundary, Suspense, native <script>

Adopt React 19 idioms across the codebase. The runtime was already on
react@19.2.5 but no React 19 APIs were in use.

- forwardRef -> ref-as-prop in 7 layout/component files
  (NitroInput/Button/ItemCountBadge/Card×5/InfiniteGridItem,
  ToolbarItemView, AvatarEditorIcon)
- <Ctx.Provider> -> <Ctx> in 6 contexts (CatalogAdmin, FloorplanEditor,
  UiSettings, GridContext, NitroCardContext, NitroCardAccordionContext)
- Native <script> hoisting for Turnstile, ExternalPluginLoader, GoogleAdsView
  (React 19 dedupes by src; removes manual document.head.appendChild +
  module-level promise caches)
- React Compiler enabled at build time via babel-plugin-react-compiler
  in vite.config.mjs (target: '19'), plus eslint-plugin-react-compiler
  in lint mode
- Global <ErrorBoundary> + <Suspense> in src/index.tsx using
  react-error-boundary, with LoadingView as fallback
- BackgroundsView migrated to use(promise) as a demonstrator pattern
  for Suspense-driven config loading
- ESLint react setting bumped 18.3.1 -> 19.2; legacy
  @typescript-eslint/ban-types replaced with no-restricted-types
  (the old rule was removed in @typescript-eslint v8)
- Refresh public/configuration/{asset-loader,bootstrap}.js to match
  current write-asset-loader.mjs output

Phase 3 (login forms -> useActionState/useFormStatus) deferred:
LoginView is 1623 lines with lockout + Turnstile + heartbeat
interleaving; safer as its own PR.

https://claude.ai/code/session_01GrR87LAqnAEyKG2ZbmQt5Q

src/layout/InfiniteGrid.tsx

@@ -1,5 +1,5 @@
 import { useVirtualizer } from '@tanstack/react-virtual';
-import { DetailedHTMLProps, Fragment, HTMLAttributes, ReactElement, forwardRef, useEffect, useRef, useState } from 'react';
+import { DetailedHTMLProps, Fragment, HTMLAttributes, ReactElement, Ref, useEffect, useRef, useState } from 'react';
 import { classNames } from './classNames';
 import { NitroLimitedEditionStyledNumberView } from './limited-edition';
 import { styleNames } from './styleNames';
@@ -150,7 +150,7 @@ const InfiniteGridRoot = <T,>(props: Props<T>) =>
     );
 };
 
-const InfiniteGridItem = forwardRef<HTMLDivElement, {
+type InfiniteGridItemProps = {
     itemImage?: string;
     itemColor?: string;
     itemActive?: boolean;
@@ -161,9 +161,11 @@ const InfiniteGridItem = forwardRef<HTMLDivElement, {
     itemUnseen?: boolean;
     itemHighlight?: boolean;
     disabled?: boolean;
-} & DetailedHTMLProps<HTMLAttributes<HTMLDivElement>, HTMLDivElement>>((props, ref) =>
+    ref?: Ref<HTMLDivElement>;
+} & DetailedHTMLProps<HTMLAttributes<HTMLDivElement>, HTMLDivElement>;
+
+const InfiniteGridItem = ({ ref, itemImage = undefined, itemColor = undefined, itemActive = false, itemCount = 1, itemCountMinimum = 1, itemUniqueSoldout = false, itemUniqueNumber = -2, itemUnseen = false, itemHighlight = false, disabled = false, className = null, style = {}, children = null, ...rest }: InfiniteGridItemProps) =>
 {
-    const { itemImage = undefined, itemColor = undefined, itemActive = false, itemCount = 1, itemCountMinimum = 1, itemUniqueSoldout = false, itemUniqueNumber = -2, itemUnseen = false, itemHighlight = false, disabled = false, className = null, style = {}, children = null, ...rest } = props;
     const [ backgroundImageUrl, setBackgroundImageUrl ] = useState<string>(null);
     const disposed = useRef<boolean>(false);
 
@@ -238,9 +240,7 @@ const InfiniteGridItem = forwardRef<HTMLDivElement, {
             { children }
         </div>
     );
-});
-
-InfiniteGridItem.displayName = 'InfiniteGridItem';
+};
 
 export const InfiniteGrid = Object.assign(InfiniteGridRoot, {
     Item: InfiniteGridItem