…rvice

Introduced alternative versions of integrity verification methods using async/await pattern instead of coroutines:
- GetApiDataAsync: Replaces GetApiData with Task-based async
- GetChecksumAsync: Replaces GetChecksum with Task-based async
- VerifyDllAsync: Replaces VerifyDll with Task-based async
- VerifyGLModAsync: Replaces VerifyGLMod with Task-based async

Benefits:
- More modern C# async pattern
- Better error handling with try/catch
- No callback-based code
- Easier to compose and test
- All methods return Task with result instead of using callbacks

Original coroutine-based methods are preserved for backward compatibility.