UI : add graceful shutdown on SIGINT/SIGTERM to prevent multiple instances being created

[PradeepSahhu]

Issue:

• When running npm run dev in the frontend directory and then stopping the terminal process using Ctrl + C , the underlying Electron app fails to shut down. Running npm run dev again spawns a new instance, resulting in multiple orphaned instances of the Electron app piling up in the macOS Dock.

Why?

• The Ctrl + C (SIGINT) command successfully kills the Vite/Node development server, but the detached Electron process ignores the signal and continues running in the background as an orphaned process.

It Doesnt fix this issue will look deep into it.