Fix configuration loading order to ensure environment variables have highest precedence over config files. Also update env prefix from CODE_ to OWLEN_ for consistency with project naming. Changes: - Move env variable merge to end of chain for proper precedence - Update environment prefix from CODE_ to OWLEN_ - Add precedence tests to verify correct override behavior - Clean up unused dependencies (serde_json, toml) - Add tempfile dev dependency for testing 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>