autoplay first episode by default, resume watched

- no ?ep= param: resume last watched ep of the season from history,
  else start at ep 1 (verified in headless Chromium, no click needed)
- if the browser blocks autoplay (no user gesture yet), show a
  'click to play' overlay instead of a silent black screen

static/style.css

@@ -23,7 +23,10 @@ h2 { margin: 0.4rem 0; }
 .detail-head { margin-bottom: 1rem; }
 .synopsis { color: var(--muted); max-width: 70ch; margin: 0.3rem 0; }
 
+.player { position: relative; }
 .player video { width: 100%; max-height: 70vh; background: #000; border-radius: 10px; aspect-ratio: 16/9; }
+.play-overlay { position: absolute; top: 50%; left: 50%; transform: translate(-50%, -50%);
+  font-size: 1.1rem; padding: 0.8rem 1.4rem; background: rgba(0, 0, 0, 0.75); }
 .controls { display: flex; align-items: center; gap: 0.4rem; margin: 0.6rem 0; }
 button { background: var(--card); color: var(--fg); border: 1px solid var(--bd);
   border-radius: 8px; padding: 0.4rem 0.7rem; cursor: pointer; }