Shutdown on Ctrl+C and SIGTERM

[Daniii44]

Before this change, the program would only exit once all spawned tasks had completed. With the new behavior, the program also quits if either Ctrl-C or SIGTERM is received. The advantage is that operations such as docker compose restart now complete almost immediately. Previously, a graceful shutdown request sent by Docker via SIGTERM had no effect, causing a 10-second wait before Docker forcefully killed the previous instance.

This solution is not perfect, since all spawned tasks are effectively terminated when the main function returns. However, it is not a step back from the previous behavior — termination now simply happens sooner.

I tested both shutdown methods and have deployed this change locally. On that note, thanks for creating this project!