Start/stop recordings with hotkey (instead of hold-to-record)

**Is your feature request related to a problem? Please describe.**
I often record long audio transcripts and find it tiring to hold the hotkey down the entire time.

**Describe the solution you'd like**
Add an option to toggle recordings with the hotkey instead of requiring press-and-hold. Press once to start recording, press again to stop.

**Describe alternatives you've considered**
I tried simulating key presses with BetterTouchTool, but it didn't work reliably and caused other side effects.

**Additional context**
Would other users be interested in this feature? I could try to implement a PR.

Start by locating the hotkey and hold-to-record handling in the legacy Swift Hex app, then verify how recording state currently changes. Done means an option supports press-once to start and press-again to stop, with the existing hold behavior preserved or clearly replaced; confirm whether work belongs in this legacy repository or the newer Rust rewrite.

Written by the indexing model from the issue text.