WebUI Architecture Cleanup (#19541)

* webui: architecture foundation (non-MCP core refactors)

* chore: update webui build output

tools/server/webui/src/lib/utils/image-error-fallback.ts

@@ -0,0 +1,10 @@
+/**
+ * Simplified HTML fallback for external images that fail to load.
+ * Displays a centered message with a link to open the image in a new tab.
+ */
+export function getImageErrorFallbackHtml(src: string): string {
+	return `<div class="image-error-content">
+		<span>Image cannot be displayed</span>
+		<a href="${src}" target="_blank" rel="noopener noreferrer">(open link)</a>
+	</div>`;
+}