Replace Spotify embeds with branded custom audio player backed by RSS

- Add /api/episode-audio route returning MP3 URLs from Anchor RSS feed
- Replace Spotify URL text inputs in admin with RSS episode dropdowns
- New EpisodeAudioPlayer component with podcast art, show name, progress
  bar, and Spotify icon link — full and compact sizes
- Backward-compatible: legacy Spotify embed URLs still render as iframes

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

server/routes/episodes.js

@@ -31,6 +31,7 @@ function parseRssItems(xml, limit = Infinity) {
     const episode = (/<itunes:episode>([\s\S]*?)<\/itunes:episode>/.exec(block)?.[1] ?? '').trim()
     items.push({
       title, pubDate, link,
+      audioUrl: enclosureUrl,
       description: descText.slice(0, 220) + (descText.length > 220 ? '…' : ''),
       duration, episode,
     })
@@ -174,4 +175,14 @@ export function register(app) {
       res.json({ episodes: episodesCache ?? [] })
     }
   })
+
+  app.get('/api/episode-audio', async (_req, res) => {
+    try {
+      const episodes = await fetchAllEpisodes()
+      res.json({ episodes: episodes.map(e => ({ title: e.title, audioUrl: e.audioUrl, duration: e.duration, episode: e.episode })) })
+    } catch (err) {
+      console.error('[episode-audio] RSS fetch error:', err.message)
+      res.json({ episodes: (episodesCache ?? []).map(e => ({ title: e.title, audioUrl: e.audioUrl, duration: e.duration, episode: e.episode })) })
+    }
+  })
 }