Batch upload form for sites / periods / cultures

In WALDO, currently the only method for uploading new entries for sites, periods, or cultures is through their respective webpages:

https://screening.reichdna.hms.harvard.edu/samples/sample_archaeology_sites
https://screening.reichdna.hms.harvard.edu/samples/sample_archaeology_periods
https://screening.reichdna.hms.harvard.edu/samples/sample_archaeology_cultures

In most external data intake cases, this suffices--we usually do not expect to need to add dozens of any of these for a single paper. Unfortunately, it turns out that there are exceptions to this rule. For example, one recent paper that was taken in was McCollWillerslevBioRxiv2025. Between 712 samples taken in, 288 sites are used. It would be extremely time-consuming to upload all 288 one-by-one in the sites webpage, and so this motivates having a way to batch upload sites. (I have not run into this issue with periods/cultures yet, but it is possible there are exceptions with these cases too.)

Start with the three existing upload pages linked in the issue: sample_archaeology_sites, sample_archaeology_periods, and sample_archaeology_cultures. Compare their current entry flows and determine how a batch submission should work for each entity; done means users can upload multiple sites, periods, or cultures without entering every item individually.