Update SPICE ingestion to use IAS remote JP2 archive

[SalimHachemaoui]

Summary

Follow-up to #508.

This updates the SPICE HVPull datasource to retrieve JP2 files directly from the IAS Helioviewer archive instead of requiring a local SPICE_DATA_PATH.

Changes

• use https://helioviewer.ias.u-psud.fr/jp2/SPICE/ as the remote SPICE datasource
• scan the supported SPICE measurement directories for each requested date
• extract observation timestamps from SPICE JP2 filenames
• poll the SPICE datasource every 60 minutes
• update SPICE ingestion tests
• update the Solar Orbiter/SPICE documentation

Remote archive layout

SPICE/YYYY/MM/DD/<measurement>/

Supported measurement directories:

774
103.19
70.38
78.77
70.6
97.25
76.51
97.7

Validation

The downloader was tested with:

python install/downloader.py \
  -d spice \
  -b http \
  -m urllib \
  -s "2026-01-01 00:00:00" \
  -e "2026-01-01 23:59:59"

The SPICE datasource initialized successfully and scanned all 8 expected measurement directories from the IAS remote archive.

[SalimHachemaoui]

Hi @dgarciabriseno , I’ve opened this PR as a follow-up to #508 to update the SPICE ingestion to use the remote IAS JP2 archive, along with the related tests and documentation.
It’s ready for review and merge when you have a chance. Thanks!