fix(docker+brain): make container Chrome search work, harden, improve toggle

Addresses review findings on the dockerized stack:
- Container Chrome search was dead: add --remote-debugging-port + a non-default
  --user-data-dir (Chrome 136+ refuses CDP on the default profile), add the
  playwright dep (browse-search.mjs connectOverCDP) with browser download
  skipped, and connect to 127.0.0.1 not "localhost" (container localhost -> ::1
  while Chrome binds IPv4). Verified: browse-search returns real results.
- Broadcast toggle reliability: always offer setBroadcast in screen-share mode
  (the embedding/keyword router dropped it for non-English utterances) and make
  its description force a tool call. "방송 꺼줘"->stop now 5/5; no false triggers.
- Stop the broadcast on voice leave (no orphaned stream).
- Security: bind VNC/noVNC to loopback by default (VNC_BIND override) and the
  bridge to the container loopback (BRIDGE_HOST=127.0.0.1), not published.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Dockerfile

@@ -8,6 +8,7 @@ FROM ubuntu:24.04
 ENV DEBIAN_FRONTEND=noninteractive \
     LANG=C.UTF-8 \
     DISPLAY=:1 \
+    PLAYWRIGHT_SKIP_BROWSER_DOWNLOAD=1 \
     PATH=/opt/venv/bin:/root/.bun/bin:/usr/local/bin:/usr/bin:/bin \
     NVIDIA_VISIBLE_DEVICES=all \
     NVIDIA_DRIVER_CAPABILITIES=compute,utility