* feat(phase2): extend ILogger interface with ILoggerRegistry

- Add logger_config structure for advanced logger configuration
- Add ILoggerRegistry interface for named logger management
- Enhance from_string() to support case-insensitive parsing
- Add support for WARN and FATAL aliases

Phase 2 Task 2.1.1: Logger Interface Unification

* feat(phase2): extend IExecutor with job-based execution

- Add IJob interface for better task control and testability
- Add execute() and execute_delayed() methods with Result<T> returns
- Keep legacy submit() methods for backward compatibility
- Add job priority and naming support

Phase 2 Task 2.2.1: Executor Interface Unification

* docs(phase2): update NEED_TO_FIX.md with Task 2.1 & 2.2 completion

- Mark Logger Interface Unification as completed
- Mark Executor Interface Unification as completed
- Update critical issues overview
- Document Phase 2 partial completion status

* fix(examples): implement execute() and execute_delayed() in mock_executor

- Add job-based execution methods to satisfy IExecutor interface
- Add calculation_job example class implementing IJob
- Add Example 7 demonstrating job-based execution
- Fixes CI build errors (abstract class instantiation)

Resolves: executor_example.cpp compilation errors

* fix(examples): use Result<T> helper functions correctly

- Use is_ok(), is_error(), get_value(), get_error() helpers
- Convert unique_ptr to shared_ptr for lambda capture
- Fixes copy-constructible requirement for std::function
- Fixes operator! and .error() usage on Result<T>

Resolves: CI compilation errors with Result<T> API