Messenger::addError() in AssetLibrary triggers page cache kill switch, making all pages uncacheable

Description:

When the Vite manifest file cannot be loaded (ManifestNotFoundException or ManifestCouldNotBeLoadedException), `AssetLibrary::getViteManifest()` calls `$this->messenger->addError()` at line 83 of `src/AssetLibrary.php`.

This triggers Drupal's `page_cache_kill_switch` service (via `Messenger::addMessage()` which calls `$this->killSwitch->trigger()`), which sets the response to `Cache-Control: must-revalidate, no-cache, private` and marks the page as `UNCACHEABLE (response policy)`. This prevents caching by both Drupal's internal page cache and any reverse proxy (Varnish, CDN).

The error is already being logged via `$this->logger->error()` on the very next line (line 84), so the messenger call is redundant for debugging purposes. The messenger error is also problematic because it surfaces an internal infrastructure error to end users, which is not useful on a production site.

Steps to reproduce:

1. Enable the vite module with a theme that uses Vite
2. Temporarily rename or delete the manifest.json file
3. Visit any page on the site
4. Check the response headers — you'll see `Cache-Control: must-revalidate, no-cache, private` and `X-Drupal-Cache: UNCACHEABLE (response policy)`
5. Restore the manifest file and visit the page again — caching works normally

Proposed fix:

Remove the `$this->messenger->addError()` call in `AssetLibrary::getViteManifest()`. The `$this->logger->error()` call on the next line already records the error for debugging. If a user-facing message is needed, it should only be shown to administrators and should not trigger the page cache kill switch.