Support for `Alt_R` Key (Right Alt) Input in WebUI for IBus Korean/English Switching

[bear8203-dev0]

Feature Request: Support for Alt_R Key (Right Alt) Input in WebUI for IBus Korean/English Switching

Environment:

• Service: nanoKVM
• OS: Ubuntu Desktop 24.04.2 (live or installed environment)
• Input method: ibus
• Use case: nanoKVM WebUI, noVNC, Windows RDP

Request:
To switch between Korean and English input using ibus on Ubuntu, the Alt_R (Right Alt) key input is required by default.
Currently, in the nanoKVM WebUI, the Alt_R key input is not properly transmitted, so ibus Korean/English switching does not work.
However, in noVNC and Windows RDP sessions at Guacamole, Alt_R switching works normally.

Reproduction Steps:

1. Connect to an Ubuntu Desktop via nanoKVM WebUI
2. Attempt to switch Korean/English input using ibus by pressing Alt_R
3. The switch does not occur (it appears that the key event itself is not recognized)
4. In the same environment, switching works normally when connected via noVNC or Windows RDP

Expected Result:

• The WebUI (nanoKVM) should properly recognize the Alt_R key input, enabling ibus Korean/English switching just like noVNC and RDP.

Additional Notes:

• This feature is essential for both Korean Windows/RDP users and Linux ibus users.
• Besides Korean/English switching, other combinations involving the Right Alt key should also be correctly transmitted.
• Please advise if any KVM configuration or patch is required.