I don't know this particular 1.6 variant well, but my first thought was front crankshaft seal. I mis-installed one on my b6 1.6. It was a little crooked. It started making noise and squealing a few months later, like a belt was going bad. It finally walked out and dumped oil on the floor of my garage.

The other thoughts were maybe something is making contact with the pulley, like one of the front engine covers. It also sounds vaguely similar to a failing air conditioning pump or bad air con pump clutch. Maybe a failing bering on the alternator. A hardened, aged accessory belt can also sing like that.

I also wanted to say EXCELLENT job documenting the sound and video!