Moves logging configuration and setup to a dedicated package. Updates Config struct to use nested LoggingConfig. Updates main.go to use the new logging package.
Adds -config CLI flag to main.go. Moves ParseLogLevel to internal/config. Adds ServerConfig nested struct to Config and corresponding tests for yaml/env overrides.
Adds internal/config package using gopkg.in/yaml.v3 and reflection for generic environment variable overrides. Updates main.go to load config and set log level. Adds tests and example config.
