read_solar_wind_from_multiple_models fails for SWOMNI

<img width="864" height="342" alt="Image" src="https://github.com/user-attachments/assets/ab111350-51f1-4170-a591-b66b98853163" />

SWOMNI has no common index with the continuous data frame and therefore only returns NaNs. The timestamps of OMNI are not full hours, but offset by 14 seconds, causing the issue. I think interpolation could fix this (see screenshot).