Player: native-HLS fallback + visible stream errors

Root cause of 'eternal spinner': a browser without working hls.js
(no MSE, or hls.min.js blocked) threw 'HLS not supported' which the
old showStreamError hid UNDER the spinner overlay, and there was no
fallback — so the player sat on Loading… forever with no /stream
request ever leaving the browser (matched the prod log exactly).

- no-hls.js + canPlayType(mpegurl)  -> v.src = proxied m3u8, native
  <video> plays it (iOS < 17 path). Verified: readyState 4, playing,
  no hls.js at all.
- no-hls.js + no native HLS        -> VISIBLE 'Stream error: ...'
  overlay with Retry (was: hidden under the spinner)
- every play() catch routes through the visible overlay now

Desktop hls.js regression: still plays. assets v=6.

static/index.html

@@ -6,7 +6,7 @@
 <title>ani-web</title>
 <link rel="icon" href="data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 64 64'%3E%3Crect width='64' height='64' rx='14' fill='%23f97316'/%3E%3Ctext x='32' y='45' font-family='sans-serif' font-size='42' font-weight='700' text-anchor='middle' fill='%230e0f13'%3Ea%3C/text%3E%3C/svg%3E">
 
-<link rel="stylesheet" href="style.css?v=5">
+<link rel="stylesheet" href="style.css?v=6">
 </head>
 <body>
 <header>
@@ -30,6 +30,6 @@
      max-age=300 in browser AND possibly in your HTTPS proxy, and a stale
      copy is exactly how users keep seeing an old UI after a deploy -->
 <script src="hls.min.js"></script>
-<script src="app.js?v=5"></script>
+<script src="app.js?v=6"></script>
 </body>
 </html>