feat: podsteadr-player — minimal browse/pay/play client for podsteadr feeds

A separate, lightweight companion app: add any podsteadr server's URL,
browse its catalog and feeds, play free episodes directly, and buy
priced ones (NIP-07 signing, Lightning invoice + QR, then playback via
the paywall-gated download-url endpoint). No backend of its own — pure
static SPA, fetches other podsteadr instances directly.

Dark glassmorphism theme matching Archipelago's own dashboard (dark
background, translucent blurred panels, orange accent).

Vite's base path is configurable via VITE_BASE (build arg / .env, not
hardcoded) so the same image can be deployed either at a dedicated
port's root (no reverse-proxy prefix) or under a subpath behind a
shared HTTPS domain, depending on the host.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.dockerignore

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+node_modules
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