Patch admin cost page so it no longer blocks other API calls

[mpkrass7]

Addresses #229

https://databricks.slack.com/archives/C0AK9GCFQMV/p1781706581725879

TL/DR there's a bunch of async routes defined for not async in the cost tab. When you define a function as async and run it, you effectively tell fastapi to run the function until it hits an await step. Then it can hand it off. Since there aren't await steps in the longer running functions, we run into this big blocking issue that makes nothing else load when you leave the tab. And you will leave the tab by the way, because these queries take a long time to run.

The claudes tell me the simple fix is to just get rid of the async defs and let fastapi figure it out in its own threadpool.
See the tldr page here: https://fastapi.tiangolo.com/async/

top spenders gets to stay defined with async since it actually does some async operations already

Network activity after fix

[mpkrass7]

Adding in:

1. Longer time to live on the cache for queries that have a long execution time
2. Make the long running queries execute at app startup so users are more likely to hit the cache visiting the cost page