Design freeform SQL query input and result table view/download features

[Ross-ROE]

Implement the archive database query and data retrieval design. Table results should provide links to FITS file downloads whenever file links provided in table results, as well as have the option to download table results as a FITS file themselves (e.g. for use in TopCat). Having a Python Django backend should help so we can presumably using the same Pyscopg3 database connector in the website backend as we use for archive curation purposes.

See also #692 for tying the schema into this page more closely, it could also have some syntax highlighting / checking / completion features.

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