v3: native bandcamp playback and a queue in the global player

The player now holds a queue instead of a single item, so albums play
through and single tracks share the same code path. Adds a "stream" item
kind for expiring, remotely-hosted sources: Bandcamp signs its mp3 URLs
for ~24h, so an item carries the page it came from and re-resolves itself
on error or on a stale restored session, falling back to the iframe embed
if that fails too.

Gated behind GERBEUR_BANDCAMP_PLAYER (default "embed"), injected into a
meta tag the same way as site-name/site-emoji.

Also: player header gains artwork and a subtitle, volume persists across
queue advances and reloads, and cross-origin streams get a plain seek bar
rather than a waveform that can never decode.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SbtjNsT5wvuABnfqhegZEJ

index.html

@@ -15,6 +15,7 @@
     <meta name="theme-color" content="#111827" />
     <meta name="site-name" content="__SITE_NAME__" />
     <meta name="site-emoji" content="__SITE_EMOJI__" />
+    <meta name="bandcamp-player" content="__BANDCAMP_PLAYER__" />
     <link rel="manifest" href="/manifest.webmanifest?v=__ICON_VERSION__" />
     <link rel="apple-touch-icon" href="/apple-touch-icon.png?v=__ICON_VERSION__" />
     <title>__SITE_NAME__</title>