Compile‑time config in config/config.exs versus runtime config in config/runtime.exs for environment‑specific values
Goal: Ensure that configuration values such as database credentials or feature flags reflect the environment where the released Elixir node runs, without requiring a new build for each change. Constraint: In a release, code in config/config.exs is executed during the mix release step, so any System.get_env/1 call captures the build‑time environment and becom