Inform users of similar initial prompts

We've seen requests for ways for people to check if they've already asked a question in particular (such as #1809), but the problem runs deeper than that. Even if you'd know all the initial prompts you've previously submitted, you still don't know if someone else has already asked the same question. I wager that there are some requests that have been made, replied to and successfully labeled multiple times now.

Ideally, we should have a system similar to Stack Overflow that goes through a database of previous initial prompts to see if someone has already made asked a question, or something very similar to it. Requests that have any number of ways to reply, such as asking for a poem, can probably stay, but a user should know that "What's a good programming language for a beginner?" or "What's the current state of AI?" can already be found in the existing prompts.

Speaking of existing prompts, maybe we can go through the backlog of initial prompts waiting in the lottery - I'm sure we can remove a good number of messages if we eliminate duplicate questions.

The issue names no files, tests, or entry points. Start by locating how initial prompts are submitted, stored, and placed in the lottery backlog; define how similar prompts should be detected, how users should be informed, and how duplicate backlog entries would be reviewed.