dealbot env vars are complicated

we should probably use a yaml/toml/json config file for configuring dealbot

**NOTE:** There is another tracking issue #118 that talks about setting backend config via front-end.. I think we need a holistic review of configuration/api needs so we can control dealbot config without needing a restart/rollout, and it would also allow filoz leaders to see/change dealbot config via an admin API of some sort. (this would get us out of gitops for config changes but could be useful for hotfix scenarios)

The issue names no files, tests, or entry points. Start by reviewing how dealbot currently receives environment variables and read tracking issue #118 for related backend configuration needs. Done requires an agreed scope for configuration storage, runtime updates, and any admin API rather than an isolated format change.

Written by the indexing model from the issue text.