fix: Improve Whisper server startup with async polling and reduce logs

- Make server startup async to avoid Bun's 10s timeout
- Add frontend polling to detect when server is ready
- Use PowerShell Get-NetTCPConnection for reliable port detection
- Add starting state to prevent multiple simultaneous starts
- Reduce verbose logging, keep only essential info
- Add dev-dist and nul to gitignore

.gitignore

@@ -3,3 +3,5 @@ frontend/node_modules/
 .env
 *.log
 dist/
+frontend/dev-dist/
+nul