* httprr: add HTTP record/replay framework with default API key scrubbing
- Add httprr package for deterministic HTTP testing
- Implement default scrubbing for common API key headers
* httputil: reorganize transport layer and add logging infrastructure
- Replace debug transports with structured logging via slog
- Add comprehensive user agent handling with version info
- Improve transport layer organization and documentation
- Maintain backward compatibility with deprecated types
- Add JSON debug transport with color output support
Travis Cline