You need an Arduino at every light.
Controlling leds with PWM can be done with a logic level power mosfet.
The problem is the power supply for the leds. They should be able to handle the PWM signal, and I don'w know if led drivers can do that.
I see this scenario: Everything seems to work so well that the lamps are mass produced and are selling good. When it is dark a person is in the shop, and the lights near him or her are on. That person uses a flashlight and switched it shortly on towards the lights above him or her. Those lights will dim, causing the lights further away in the shop to turn on. This starts a never ending wave of oscillation lights across the whole town.