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/NitroButton.tsx

@@ -1,4 +1,4 @@
-import { ButtonHTMLAttributes, DetailedHTMLProps, forwardRef, PropsWithChildren } from 'react';
+import { ButtonHTMLAttributes, DetailedHTMLProps, PropsWithChildren, Ref } from 'react';
 import { classNames } from './classNames';
 
 const classes = {
@@ -17,14 +17,15 @@ const classes = {
     }
 };
 
-export const NitroButton = forwardRef<HTMLButtonElement, PropsWithChildren<{
+type NitroButtonProps = PropsWithChildren<{
     color?: 'default' | 'dark' | 'ghost';
     size?: 'default' | 'lg' | 'xl';
     outline?: boolean;
-}> & DetailedHTMLProps<ButtonHTMLAttributes<HTMLButtonElement>, HTMLButtonElement>>((props, ref) =>
-{
-    const { color = 'default', size = 'default', outline = false, disabled = false, type = 'button', className = null, ...rest } = props;
+    ref?: Ref<HTMLButtonElement>;
+}> & DetailedHTMLProps<ButtonHTMLAttributes<HTMLButtonElement>, HTMLButtonElement>;
 
+export const NitroButton = ({ ref, color = 'default', size = 'default', outline = false, disabled = false, type = 'button', className = null, ...rest }: NitroButtonProps) =>
+{
     return (
         <button
             ref={ ref }
@@ -39,6 +40,4 @@ export const NitroButton = forwardRef<HTMLButtonElement, PropsWithChildren<{
             type={ type }
             { ...rest } />
     );
-});
-
-NitroButton.displayName = 'NitroButton';
+};