fix(widgets): stop silently discarding invalid JSON edits in the props fallback textarea

updateJson() caught JSON.parse failures and did nothing, but the textarea
was bound to propsJson(committed props) - so on the next change-detection
pass, any in-progress invalid edit snapped back to the last-saved value
with zero feedback. Verified live via window.ng.getComponent(): typing
invalid JSON now keeps the user's draft on screen with an inline error;
fixing it commits and clears the draft/error.

Also: homepage-section drop() used CdkDragDrop<any[]> - switched to
unknown[] per the no-any rule, no behavior change.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/i18n/en.ts

@@ -658,6 +658,7 @@ export const en: Translations = {
     widgetShowRatingDesc: 'Show the star rating on product cards.',
     widgetShowPriceDesc: 'Show the price on product cards.',
     widgetJsonDesc: 'Raw widget properties as JSON. Used when no dedicated editor exists for this widget type.',
+    widgetJsonInvalid: 'Invalid JSON - the last valid version is still saved.',
     wishlistFeatureDesc: 'Let shoppers save products to a wishlist.',
     compareFeatureDesc: 'Let shoppers compare multiple products side by side.',
     reviewsFeatureDesc: 'Let shoppers leave and read product reviews.',