refactor(i18n): update remote control copy and default port

Update English translations for the remote-control UI and change the
documented default remote-control port.

- Change default remote control port description from 3000 to 8765 to
  reflect actual configuration.
- Improve remote control UI copy:
  - Add SUBTITLE "Control your IPTV player remotely".
  - Capitalize UP_CHANNEL and DOWN_CHANNEL labels to "Channel Up" and
    "Channel Down" for consistent UI presentation.

These changes clarify the feature and align text with current behavior.

Author: 4gray