Growth features: share buttons, NEW badge, sticky CTA, newsletter cross-promote

- Share buttons on episode and clip cards (Web Share API + clipboard fallback)
- NEW badge on latest episode card
- Sticky call-in CTA bar (appears after hero scrolls out)
- Daily AI Briefing newsletter cross-promote in footer
- Bump cache versions to v=5

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

website/how-it-works.html

@@ -28,7 +28,7 @@
   <link rel="apple-touch-icon" href="apple-touch-icon.png">
 
   <link rel="alternate" type="application/rss+xml" title="Luke at the Roost RSS Feed" href="https://podcast.macneilmediagroup.com/@LukeAtTheRoost/feed.xml">
-  <link rel="stylesheet" href="css/style.css?v=4">
+  <link rel="stylesheet" href="css/style.css?v=5">
 
   <!-- Structured Data -->
   <script type="application/ld+json">