- Replace global ConfigPath and Overrides with viper-based configuration
- Add viper.New() to create configurable viper instances
- Store viper and unmarshaled Config struct in context for testability
- Add RetrieveFromContext and AddToContext helper functions
- Update files.Append to accept context and retrieve config from it
- Update formatters.Preferred and formatters.New to accept context
- Add PersistentPreRunE in CLI to create and configure viper instance
- Support -c flag for custom config file path
- Support -v flag for config value overrides
- Update all test files to create viper and add to context
- Remove unused config types and load functions
- Add viper as dependency with automatic env var support (MYLOG_*)
- Replace all testify/assert and testify/require with be library
- Update go.mod to use be v0.3.0 instead of testify
- Simplify test assertions using be.Equal, be.Err, and be.True
- Refactor append_test, entry_test, meta_test, log_test, and formatter tests
