Is there still a need for a solar system at all with air-water heat pumps and photovoltaics?

Can be done, but it is more common to use a heat pump for both.

say the one air-water heat pump operates both in two different circuits / water tanks: 1) for the underfloor heating 30 °C 2) for domestic hot water 60 °C both ideally during the day with photovoltaic power from the roof.

Exactly, it switches between the circuits with a valve. For showering, about 40° is sufficient. My heat pump can go up to 55°, but that becomes inefficient. It makes sense to have low temperatures in the storage, up to about 50°, and regular use of the water: storage not too large and dependent on personal consumption.

I would have suggested 60° because of Legionella. We don't need that for showering either. 40° is really enough. But the risk in a single-family house is rather very low, right?

a) low temperatures, properly sized hot water storage tank with regular usage
b) high storage temperatures or regular legionella prevention program
c) fresh water station

In a single-family house, the risk does not seem too high, but legionella multiply at temperatures below 50°/55°.
You have to decide for yourself.

To avoid constantly heating the water inefficiently to 60 degrees, many heat pumps also have a Legionella program, for example, to run once a week. The rest of the time, one then uses around 45 degrees.