Move from a rough heuristic (# of api calls per day) to actual dollar limits, so:

1. It's more legible to users
2. More legible to us
3. Clearer that we're not losing money on this

1. Merge branch to main — merge_branch on dollar-rate-limiting
2. Set custom subdomain — set_custom_subdomain on proxy/main.ts with subdomain std-openaiproxy and force: true (this is the actual cutover — every existing SDK import instantly hits the new proxy)
3. Update main.ts SDK baseURL — Change back to https://std-openaiproxy.web.val.run/v1 (currently points at the branch's file-hash URL for testing)
4. Confirm we're not seeing lots of errors on std/openaiproxy or the new proxy
5. Archive std/openaiproxy