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/components/backgrounds/BackgroundsView.tsx

@@ -1,4 +1,4 @@
-import { Dispatch, FC, SetStateAction, useCallback, useEffect, useMemo, useState } from 'react';
+import { Dispatch, FC, SetStateAction, use, useCallback, useMemo, useState } from 'react';
 import { Base, Grid, Flex, NitroCardView, NitroCardHeaderView, NitroCardTabsView, NitroCardTabsItemView, NitroCardContentView, Text } from '../../common';
 import { useRoom } from '../../hooks';
 import { GetOptionalConfigurationValue } from '../../api';
@@ -25,6 +25,20 @@ type TabType = typeof TABS[number];
 
 type RemoteData = Partial<Record<'backgrounds.data' | 'stands.data' | 'overlays.data' | 'cards.data', any[]>>;
 
+let backgroundsDataPromise: Promise<RemoteData | null> | null = null;
+
+const fetchBackgroundsData = (): Promise<RemoteData | null> =>
+{
+    if(backgroundsDataPromise) return backgroundsDataPromise;
+
+    backgroundsDataPromise = fetch(configFileUrl('infostand_backgrounds.json'), { credentials: 'omit' })
+        .then(r => r.ok ? r.json() : null)
+        .then(json => (json && typeof json === 'object') ? json as RemoteData : null)
+        .catch(() => null);
+
+    return backgroundsDataPromise;
+};
+
 export const BackgroundsView: FC<BackgroundsViewProps> = ({
     setIsVisible,
     selectedBackground,
@@ -37,18 +51,9 @@ export const BackgroundsView: FC<BackgroundsViewProps> = ({
     setSelectedCardBackground
 }) => {
     const [activeTab, setActiveTab] = useState<TabType>('backgrounds');
-    const [remoteData, setRemoteData] = useState<RemoteData | null>(null);
+    const remoteData = use(fetchBackgroundsData());
     const { roomSession } = useRoom();
 
-    useEffect(() => {
-        let cancelled = false;
-        fetch(configFileUrl('infostand_backgrounds.json'), { credentials: 'omit' })
-            .then(r => r.ok ? r.json() : null)
-            .then(json => { if(!cancelled && json && typeof json === 'object') setRemoteData(json as RemoteData); })
-            .catch(() => {});
-        return () => { cancelled = true; };
-    }, []);
-
     const processData = useCallback((configData: any[], idField: string): ItemData[] => {
         if (!configData?.length) return [];