What should I validate before starting development of a new iOS app?

I take a lot of screenshots such as tickets, ideas, chats, and receipts, but I often forget about them later, so I am considering building an iOS app that asks the purpose of a screenshot as soon as it is taken, lets you assign it to a category, and reminds you after a set number of days to turn screenshots into actions instead of clutter.

Before starting development, I would love to know if this feels genuinely useful, whether you would consider paying around $2 per month for it, and what features you would like to see, as I truly appreciate any honest feedback.

What should I validate before starting development of a new iOS app?
 
 
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