Feature Request: Pause and resume recordings

**Is your feature request related to a problem? Please describe.**
Sometimes mid-recording I need to collect my thoughts, take a quick break, or wait for background noise to pass. Right now the only option is to cancel and start over, which means losing everything I've recorded so far.

**Describe the solution you'd like**
The ability to pause and resume recordings:
- Pause the recording temporarily (visual indicator changes to show paused state)
- Resume recording when ready
- Final transcript combines all recorded segments seamlessly

**Describe alternatives you've considered**
I've tried keeping quiet during pauses, but this often results in placeholder text like "Thank you" being inserted into the transcription. Canceling and restarting loses all progress.

**Additional context**
This would be especially helpful for longer dictations where restarting from scratch isn't ideal — for example when recording meeting notes, drafting emails, or dictating longer texts.

Start by checking the legacy Swift Hex app and its recording and transcription entry points; no files or tests are named in the issue. Before implementing, verify whether this belongs in the legacy app or the Rust rewrite referenced in the repository description, then confirm that pause/resume preserves segments, updates the visual state, and produces one combined transcript.

Written by the indexing model from the issue text.