NethVoice CTI: Duplicate "User Busy" notification when both NethLink and NethCTI are open

[mgarra]

Description:
When calling a busy user, the Phone Island notification is displayed twice if both NethLink and NethCTI are open at the same time.

• The notification coming from NethLink is correct.
• The one triggered by NethCTI shows partial information.

Steps to reproduce:

1. Open both NethLink and NethCTI.
2. Make a call to a user who is currently busy.
3. Observe that two Phone Island notifications appear.

Expected behavior:
Only one notification should be displayed, containing the correct information.

Additional note:
Please also check translations of busy user notifications.
When logged in only through NethCTI (with NethLink closed), the interface labels appear in English, even if both the browser and the system are set to Italian.

[tonyco97]

Testing version: https://github.com/nethesis/ns8-nethvoice/releases/tag/1.4.6-testing.3