Feature request: Auto-send feature

**Is your feature request related to a problem? Please describe.**
Since modern speech-to-text models provide high accuracy, we can streamline the process of sending the message by enabling automatic sending of transcribed text.

**Describe the solution you'd like**
Add an auto-send feature that automatically sends transcribed text to the active application once transcription completes. The solution could include configurable keyboard shortcuts for auto-sending:
* Press Enter alone
* Press Command + Enter
* Press Shift + Enter

**Describe alternatives you've considered**
* Manual sending after each transcription (current workflow)

**Additional context**
Extra: Aditionaly, incorporing a live transcription preview window that display text in real-time as users dictate would allow users to:
* Monitor transcription accuracy while speaking
* Detect errors before auto-sending
* Decide whether to auto-send or edit before sending

**Use case example**
In a messaging app, transcribed text sends automatically.

**This feature would significantly improve workflow efficiency for users who frequently use dictation in messaging and communication applications, such as chatbots and messaging apps.**

Start by locating where transcription completes and where text is sent to the active application. Clarify whether auto-send shortcuts, configurable behavior, and the live preview are all in scope, then check the referenced Rust rewrite before starting. Done means the agreed sending behavior and preview workflow are implemented and verified.

Written by the indexing model from the issue text.