The B3 streaming proxy endpoint existed in the backend but nginx had no
location for /api/peer-content/*, so the browser's requests fell through to
the SPA (200 text/html) and media still wouldn't play. Add an
NGINX_PEER_CONTENT_BLOCK that bootstrap patches into every server block
(forwards Cookie for session auth + Range, proxy_buffering off). Idempotent;
covers fresh-ISO nodes too since bootstrap runs on every startup.
Verified on .198: after restart the async nginx patch lands and
/api/peer-content/<onion>/<id> returns 401 (reaches backend, auth-gated)
instead of the SPA; nginx block present in both server blocks.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>