Restructure solution layout by module

src/__Libraries/StellaOps.Cryptography.DependencyInjection/CryptoProviderRegistryOptions.cs

@@ -0,0 +1,14 @@
+using System.Collections.Generic;
+
+namespace StellaOps.Cryptography.DependencyInjection;
+
+/// <summary>
+/// Options controlling crypto provider registry ordering and selection.
+/// </summary>
+public sealed class CryptoProviderRegistryOptions
+{
+    /// <summary>
+    /// Ordered list of preferred provider names. Providers appearing here are consulted first.
+    /// </summary>
+    public IList<string> PreferredProviders { get; } = new List<string>();
+}