Production fixes: modal stays open, gradient UI, source links, stepper cleanup

- Fixed progress modals closing prematurely during analysis/research
- Enhanced Create Your Voice Clone button with gradient styling
- Light gradient themes for Expert Quotes, Listener CTAs, Mapped Angles
- Made source reference chips clickable with links in new tab
- Removed duplicate stepper (kept in Header only)
- Skip api-stats endpoint in podcast-only mode
- Combined 3 voice scripts into 1 example
- Added force-include step4_assets router in podcast mode

frontend/src/services/podcastApi.ts

@@ -213,10 +213,17 @@ const mapExaResearchResponse = (response: any): Research => {
     mappedFactIds: angle.mapped_fact_ids || angle.mappedFactIds || []
   }));
 
+  const sources = (response.sources || []).map((source: any) => ({
+    title: source.title || "",
+    url: source.url || "",
+    excerpt: source.excerpt || source.highlights?.[0] || ""
+  }));
+
   return {
     summary,
     keyInsights,
     factCards,
+    sources,
     mappedAngles,
     expertQuotes,
     listenerCta,