fix: Restructure HashComputation to root level for proper exports

Moved HashComputation types from nested Algorithms/Cryptography/ directory
to root Sources/DesignAlgorithmsKit/ directory. This makes types directly
accessible as DesignAlgorithmsKit.HashComputation without needing @_exported.

Swift's module system doesn't support @_exported import for same-module enums,
so moving to root level is the proper solution.

Changes:
- Moved Sources/DesignAlgorithmsKit/Algorithms/Cryptography/HashComputation.swift
  to Sources/DesignAlgorithmsKit/HashComputation.swift
- Moved Tests/DesignAlgorithmsKitTests/Algorithms/Cryptography/HashComputationTests.swift
  to Tests/DesignAlgorithmsKitTests/HashComputationTests.swift
- Updated version: 1.2.0 → 1.2.1
- All 149 tests passing

Fixes FileSystemKit integration issue where types weren't accessible.

Version: 1.2.1

Author: rickhohler

Sources/DesignAlgorithmsKit/DesignAlgorithmsKit.swift

@@ -51,7 +51,7 @@ import Foundation
 /// - WASM (limited - excludes hash/crypto types that require NSLock)
 public struct DesignAlgorithmsKit {
     /// Library version
-    public static let version = "1.2.0"
+    public static let version = "1.2.1"
 }
 
 // Re-export all modules