Some dataset requests are duplicated

### Context

https://github.com/AlexsLemonade/refinebio/issues/2801 and https://github.com/AlexsLemonade/refinebio/issues/2802

### Problem or idea

It looks like we have some dataset requests that are duplicated. My two main hypotheses are:
- Our form doesn't give enough feedback that it has successfully been submitted, so people submit more than once
- I haven't actually looked at the form for a while, so this definitely could be false
- We have some issue on the backend that duplicates these requests

### Solution or next step

Look into the two hypotheses to see if either could be a reasonable explanation.

Start by reviewing issues 2801 and 2802, then inspect the dataset request form and the backend submission path mentioned in the issue. Check whether users receive enough submission feedback and whether the backend can duplicate requests. Done means determining whether either hypothesis reasonably explains the duplicates and documenting the evidence.

Written by the indexing model from the issue text.