Add SPASSO data fetching and visualization

[LOCEANlloydizard]

this PR adds support for fetching and visualizing SPASSO products in echodataflow.

It adds:

• a Prefect flow to incrementally download remote-sensing and diagnostic products from SPASSO over SFTP
• selection of the latest available file independently for each configured product family, while skipping products already available locally
• a visualization service linking the downloaded SPASSO products with ship navigation (GPS from the ship), including environmental remote-sensing products, surface currents, and fine-scale diagnostics
• configuration of products, paths, and visualization parameters outside echodataflow, allowing the workflow to be adapted to different cruises (e.g. in echodataflow-recipes)
• tests for the SPASSO fetching flow and SFTP operations.

Refs for SPASSO:

Rousselet, L., d’Ovidio, F., Izard, L., Della Penna, A., Petrenko, A., Barrillon, S., Nencioli, F. and Doglioli, A. (2025). A Software Package for an Adaptive Satellite-Based Sampling for Oceanographic Cruises (SPASSOv2.0): Tracking Fine-Scale Features for Physical and Biogeochemical Studies. Journal of Atmospheric and Oceanic Technology, 42(8), 979–990.