Sun and wind sensors for venetian blinds and roller shutter control

1000 euros is not little. I would always go for z-Z-Wave if no wired solution is possible or desired. Because it offers similar functions and similar interoperability as professional solutions. Here just check whether a stick with a Pi is enough or if a central unit is necessary.

that one might only use the function to lower all shutters/blinds before going to bed.

But you can basically achieve that without any "systems" just with the switches of the preferred switch/motor manufacturer which have an astro function and at the same time can of course manage several switching times.

You don't need a phone or anything overarching for that, and it was already possible even back when Helmut Kohl was Chancellor without major problems. But that's just by the way.

that you can control such things with a Raspberry PI as well.

The Pi or also a NUC or something else basically only offers a software platform. You still need the infrastructure (hardware) which is to be operated and which then provides the sensor data.

Sure, you can also tinker a lot with that, but that rather drifts into the DIY area and nowadays you can just as easily use ready available tools and devices.

Nevertheless, I also have a Pi in the HAR as a secondary system, which also provides access to the house (via SmarthomeNG) and through which everything can be controlled. So if you enjoy it, you can already do quite a bit with it.

A button is always included in the delivery scope for Somfy motors. If you do not want to control the all up/down function via the smartphone, simply buy an additional button and teach it to all motors. The advantage of Somfy is the constant expandability of the system and, of course, the support.