Enable "Cold Transfer" Hashtag (##) support for Presence/BLF Keys

Description:
Currently, when configuring a Presence (BLF) key for a colleague on a Mitel 6930 (or any RingCentral-provisioned desk phone), the system only allows for a standard extension number. There is a critical need to allow DTMF characters, specifically the double hashtag (##), to be prepended to the extension within the Presence field.

Current Pain Point:
Users want to perform a One-Touch Cold Transfer.

If a user manually programs a Speed Dial on the phone as ##[Ext], it works perfectly.

However, if they use the Presence feature via the Admin Portal, they cannot add ##. This forces the phone to perform a "Consultative" transfer by default, requiring multiple extra button presses to complete a simple transfer.

Manual local programming on the phone is not a viable workaround because it is overwritten by the RingCentral Resync/Provisioning server.

Desired Behavior:
Allow the "Extension Number" field in the Presence settings to accept characters like #, *, and , (pause). This would allow an admin to set a key as ##101. The phone would then show the "Presence" (Red/Green status) of extension 101, but when pressed during an active call, it would send the ## command to trigger a Blind Transfer immediately.