Improve code structure

- Add separate API project
- Add notification system

HyperbolicDownloaderApi/FileProcessing/FileValidator.cs

@@ -0,0 +1,29 @@
+using System.Security.Cryptography;
+
+namespace HyperbolicDownloaderApi.FileProcessing;
+
+internal static class FileValidator
+{
+    public static async Task<string> CalculateHashAsync(string filePath)
+    {
+        using SHA512 sha = SHA512.Create();
+        using FileStream? stream = File.OpenRead(filePath);
+        byte[]? hash = await sha.ComputeHashAsync(stream);
+        return BitConverter.ToString(hash).Replace("-", "").ToLowerInvariant();
+    }
+
+    public static string CalculateHash(string filePath)
+    {
+        return CalculateHashAsync(filePath).GetAwaiter().GetResult();
+    }
+
+    public static async Task<bool> ValidateHashAsync(string filePath, string hash)
+    {
+        return await CalculateHashAsync(filePath) == hash;
+    }
+
+    public static bool ValidateHash(string filePath, string hash)
+    {
+        return CalculateHash(filePath) == hash;
+    }
+}