Windows subprocess timeout cleanup still breaks in last30days.py and bird_x.py

I ran into this on Windows while debugging YouTube access locally.

I had already fixed one subprocess cleanup path in the YouTube code, but while reproducing that issue I noticed there are still other timeout/cleanup paths that use Unix-only logic like os.killpg(os.getpgid(pid), signal.SIGTERM).

I found at least these remaining spots:

• scripts/last30days.py
• scripts/lib/bird_x.py

So this looks like the same cross-platform bug still exists in a few other subprocess paths.

What I saw

On Windows, subprocess timeout cleanup can still break when these Unix-specific APIs are used directly.

Suggested fix

It probably makes sense to use the same cross-platform cleanup pattern everywhere:

• use killpg/getpgid only when available
• otherwise fall back to proc.kill() (or another Windows-safe termination path)

That should make subprocess timeout/cleanup behavior more consistent across platforms.