feat(whispering): add system default microphone with auto device detection

[thisisharsh7]

Summary

Adds a "System Default" microphone option that automatically tracks the OS default input device, with automatic device list updates when devices are plugged/unplugged. Fixes the issue where users had to manually select their microphone every time they plugged/unplugged devices, preventing lost recordings from forgotten device selection.

Type of Change

• feat: New feature
• fix: Bug fix
• docs: Documentation update
• refactor: Code refactoring (no functional changes)
• perf: Performance improvement
• test: Test additions or changes
• chore: Maintenance tasks
• style: Code style changes

Related Issue

Closes #1246

Changes Made

• Integrated device change listener with auto-refresh when popover is open
• Added "Auto" badge to "System Default" option
• Device lists now update automatically on plug/unplug

Testing

Desktop App Testing

• Tested on macOS
• Tested on Windows
• Tested on Linux
• Not applicable (web-only change)

General Testing

• Tested with multiple API providers (if applicable)
• Verified no API keys are exposed in logs or storage
• Checked for console errors
• Tested on different screen sizes (if UI change)

Checklist

• My code follows the project's coding standards (see CONTRIBUTING.md)
• I've used type instead of interface in TypeScript
• I've used absolute imports where applicable
• I've tested my changes thoroughly
• I've added/updated tests for my changes (if applicable)
• My changes don't break existing functionality
• I've updated documentation (if needed)