fix: pass source event to RichText in highlight feed preview

The source event preview in HighlightRenderer was only passing the
content string to RichText, which meant custom emoji tags from the
source event weren't processed. Now passes the source event with
the preview content to enable proper emoji and tag-based rendering.

src/components/nostr/kinds/HighlightRenderer.tsx

@@ -100,7 +100,7 @@ export function Kind9802Renderer({ event }: BaseEventProps) {
                 onClick={handleOpenEvent}
               >
                 <RichText
-                  content={sourcePreview}
+                  event={{ ...sourceEvent, content: sourcePreview }}
                   options={{ showMedia: false, showEventEmbeds: false }}
                 />
               </div>