.env shrinks to bootstrap values only (port, paths, log, auth, deploy
flags). The 14 admin-tunable values (retention, whisper, ollama, llm)
move to a new settings.toml with serde(default)-based per-section
defaults and an empty-prompt fallback to the code default. settings.toml
is gitignored alongside .env; settings.toml.example is the template.
This commit fixes the file layout. The server-side wiring (Config shrink,
AppState integration, consumer migration) follows separately.
