Allow Switching to Handsfree Mode Mid-Recording

Currently, in Vowen, handsfree mode can only be activated at the start of a recording. If I begin with the transcription hotkey, I cannot switch to handsfree without stopping and starting a new recording. Coming from Wisperflow, pressing the Fn key and then the bar button allowed seamless transition to handsfree mid-session. Adding similar functionality in Vowen would improve workflow and flexibility.

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