feat: add Codex fast mode configuration and handling

- Introduced a new `fast-mode.ts` file to manage Codex fast mode settings.
- Updated `Inbound_Provider` to read fast mode configuration and adjust request normalization accordingly.
- Enhanced `normalizeRequestBody` and `normalizeCanonicalRequest` to include service tier metadata.
- Added UI components for toggling fast mode in the application.
- Implemented tests for fast mode configuration reading and writing, as well as its effect on request handling.