feat(demo): real registry UIs, IndeeHub iframe proxy, mempool tab, media Range

- App UIs now use the real registry shells with dummy data: bitcoin-ui for
  Bitcoin Core (Satoshi subversion) and Bitcoin Knots (Knots subversion) via
  per-path /app/bitcoin-{core,knots}/bitcoin-status; the real lnd-ui (mock
  /proxy/lnd/v1/getinfo+channels, /lnd-connect-info, /api/container/logs); the
  static fedimint-ui. ElectrumX already on the real electrs-ui. Custom mock UIs
  dropped — accurate UX.
- IndeeHub loads in the iframe: nginx reverse-proxies /app/indeedhub/ →
  indee.tx1138.com and strips X-Frame-Options/CSP (it blocked framing before).
- Mempool opens in a new tab (mempool.space can't be iframed).
- Cloud media playback: HTTP Range support in the curated-file server so audio/
  video can stream and seek (needs real files dropped into demo/files/).
- Dockerfile/.dockerignore copy docker/lnd-ui + docker/fedimint-ui.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

neode-ui/Dockerfile.backend

@@ -18,6 +18,8 @@ COPY neode-ui/ ./
 # the Bitcoin UI mock shell and any curated cloud files dropped into demo/files.
 COPY docker/bitcoin-ui /docker/bitcoin-ui
 COPY docker/electrs-ui /docker/electrs-ui
+COPY docker/lnd-ui /docker/lnd-ui
+COPY docker/fedimint-ui /docker/fedimint-ui
 COPY demo/files /demo/files
 
 # Expose port