Per-shortcut auto-submit control

[parichay28]

Auto-submit is currently a global setting that fires immediately after transcription. Different workflows naturally call for different behaviours:

• Dictating into a notepad or document — paste and move on, no review needed.
• Dictating a Slack message or PR comment — paste, review, then send.

A dedicated submit shortcut would give users explicit control over this. After transcription (with or without post-processing), the user can optionally press a separate shortcut to submit using whichever keystroke is already configured in the existing dropdown (Enter, Cmd+Enter, etc.). If no explicit shortcut is pressed, the text simply stays pasted for review.

This keeps the existing auto-submit setting intact for users who prefer the current behaviour, while giving others a more deliberate workflow.