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

package.json

@@ -23,6 +23,7 @@
         "framer-motion": "^12.38.0",
         "react": "^19.2.5",
         "react-dom": "^19.2.5",
+        "react-error-boundary": "^6.1.1",
         "react-icons": "^5.5.0",
         "react-player": "^2.16.0",
         "use-between": "^1.4.0"
@@ -36,8 +37,10 @@
         "@typescript-eslint/eslint-plugin": "^8.59.1",
         "@typescript-eslint/parser": "^8.59.1",
         "@vitejs/plugin-react": "^6.0.1",
+        "babel-plugin-react-compiler": "^1.0.0",
         "eslint": "^10.2.1",
         "eslint-plugin-react": "^7.37.5",
+        "eslint-plugin-react-compiler": "19.1.0-rc.2",
         "eslint-plugin-react-hooks": "^7.1.1",
         "postcss": "^8.5.12",
         "postcss-nested": "^7.0.2",