mobile: add a phone dashboard on a second port (8443) — Live + Archive

A new mobile dashboard is served on a second host port (8443) mapped to the
same backend, so the recorder/supervisor is not duplicated. main.py detects
the mobile port via the Host header and serves mobile.html instead of the
desktop index. The mobile SPA has two modes: Live (one camera with a selector)
and Archive (camera + date + segment list). Video is delivered as server-side
H.264 (live.mp4 / play.mp4 transcode) so a plain <video> plays on any phone.
Bottom tab bar, dark theme, safe-area aware.

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

docker-compose.yml

@@ -10,7 +10,8 @@ services:
     command: ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8090",
               "--ssl-keyfile", "/app/certs/key.pem", "--ssl-certfile", "/app/certs/cert.pem"]
     ports:
-      - "443:8090"                # дашборд на https://<сервер>
+      - "443:8090"                # десктоп-дашборд на https://<сервер>
+      - "8443:8090"               # мобильный dashboard https://<сервер>:8443 (тот же бэкенд, mobile.html по Host)
     volumes:
       - ./certs:/app/certs                    # self-signed TLS-сертификат (rw: entrypoint генерирует при отсутствии)
       - ./VERSION:/app/VERSION:ro             # номер версии (показывается в UI)