Add BunnyCDN integration, on-air website badge, publish script fixes

- On-air toggle uploads status.json to BunnyCDN + purges cache, website
  polls it every 15s to show live ON AIR / OFF AIR badge
- Publish script downloads Castopod's copy of audio for CDN upload
  (byte-exact match), removes broken slug fallback, syncs all episode
  media to CDN after publishing
- Fix f-string syntax error in publish_episode.py (Python <3.12)
- Enable CORS on BunnyCDN pull zone for json files
- CDN URLs for website OG images, stem recorder bug fixes, LLM token
  budget tweaks, session context in CLAUDE.md

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

website/js/app.js

@@ -300,6 +300,24 @@ function initTestimonials() {
   resetAutoplay();
 }
 
+// On-Air Status
+function checkOnAir() {
+  fetch(`https://cdn.lukeattheroost.com/status.json?_=${Date.now()}`)
+    .then(r => r.json())
+    .then(data => {
+      const badge = document.getElementById('on-air-badge');
+      const offBadge = document.getElementById('off-air-badge');
+      const phone = document.getElementById('phone-section');
+      const live = !!data.on_air;
+      if (badge) badge.classList.toggle('visible', live);
+      if (offBadge) offBadge.classList.toggle('hidden', live);
+      if (phone) phone.classList.toggle('live', live);
+    })
+    .catch(() => {});
+}
+
 // Init
 fetchEpisodes();
 initTestimonials();
+checkOnAir();
+setInterval(checkOnAir, 15000);