Migrate to pnpm

[bliuchak]

We need to enable features like minimum release age enforcement to prevent us from being hit by supply chain attacks. NPM does not support this, therefore we need to switch to PNPM.

[jancurn]

@B4nan might have a skill for that?

[B4nan]

I had a long-running session, which I managed to clear just a few hours ago :D But I already have some fresh context there about the mcp server migration, let me ask it to PR proxy chain, too.