Add per-episode play tracking with bar chart in admin analytics

- POST /api/analytics/play records a play event (title + date) on first
  play per player mount, skipping admin sessions
- Plays persisted to data/episode-plays.json with total + byDay buckets
- Admin stats response includes episodePlays sorted by total plays
- AnalyticsPanel shows horizontal bar chart + summary cards for all
  episodes dynamically — new episodes appear automatically as played

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

src/components/EpisodeAudioPlayer.tsx

@@ -35,6 +35,7 @@ export function EpisodeAudioPlayer({ src, title, size = 'full', spotifyUrl }: Ep
   const [playing, setPlaying] = useState(false)
   const [currentTime, setCurrentTime] = useState(0)
   const [duration, setDuration] = useState(0)
+  const playTrackedRef = useRef(false)
 
   useEffect(() => {
     const audio = audioRef.current
@@ -61,7 +62,17 @@ export function EpisodeAudioPlayer({ src, title, size = 'full', spotifyUrl }: Ep
       audio.pause()
       setPlaying(false)
     } else {
-      audio.play().then(() => setPlaying(true)).catch(() => {})
+      audio.play().then(() => {
+        setPlaying(true)
+        if (!playTrackedRef.current && title) {
+          playTrackedRef.current = true
+          fetch('/api/analytics/play', {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/json' },
+            body: JSON.stringify({ title }),
+          }).catch(() => {})
+        }
+      }).catch(() => {})
     }
   }