Fix potential bugs: improve exception handling, destructors, and cache management

[Copilot]

This PR addresses several potential bugs and improves code robustness in the design patterns implementation:

Issues Fixed

1. Improper Exception Usage

Replaced deprecated std::exception() with more specific std::runtime_error with descriptive messages:

// Before
throw std::exception();

// After  
throw std::runtime_error("Key already registered in factory");

This affects 6 locations across factory.h and memoize.h, providing better error diagnostics.

2. Destructors Throwing Exceptions

Fixed destructors in factory_registrator and memoize_registrator that could throw exceptions, violating C++ best practices:

// Before
~factory_registrator() {
    _f.template unregister_type<U>();
}

// After
~factory_registrator() {
    try {
        _f.template unregister_type<U>();
    } catch (...) {
        // Destructors should not throw exceptions
    }
}

3. Inconsistent Cache Management

Improved cache consistency in the memoize class by ensuring both _map_cache (weak_ptr) and _map_cache_shared (shared_ptr) are managed together:

// Before: only cleared shared cache
void clear() const {
    _map_cache_shared.clear();
}

// After: clear both caches for consistency
void clear() const {
    _map_cache.clear();
    _map_cache_shared.clear();
}

4. Thread Safety Documentation

Added explicit warnings about thread safety requirements, as these classes use mutable containers without synchronization.

5. Build Configuration

Updated .gitignore to properly exclude node_modules/ and build artifacts.

Testing

The changes maintain backward compatibility and don't affect the public API. All existing tests should continue to pass as the fixes address potential runtime issues and improve error handling without changing functionality.

These improvements make the codebase more robust, follow C++ best practices, and provide better debugging information when issues occur.

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