Virtual keyboard button is not always shown when needed

[LMattsson]

Describe the bug
For example, Oculus Quest 3 does not have a physical keyboard, but noVNC does not show the virtual keyboard button in the built-in browser.

To Reproduce
Steps to reproduce the behavior:

1. Open the built-in browser on Oculus Quest 3
2. Log in using noVNC
3. Note the missing button

Expected behavior
Should correctly identify when a physical keyboard is missing.

Screenshots
Screenshots taken from issue #1832:

Client (please complete the following information):

• OS: Oculus Quest 3 V60
• Browser: Default/Intern

Server (please complete the following information):

• noVNC version: master as of 2024-01-22
• VNC server: gnome-remote-desktop
• WebSocket proxy: websockify

Additional context

The usual media queries we use here are not helpful in this case. It seems the browser lies to us.

[LMattsson]

One idea is to add an option for showing the virtual keyboard in cases like these.