Add Authority Advisory AI and API Lifecycle Configuration

- Introduced AuthorityAdvisoryAiOptions and related classes for managing advisory AI configurations, including remote inference options and tenant-specific settings.
- Added AuthorityApiLifecycleOptions to control API lifecycle settings, including legacy OAuth endpoint configurations.
- Implemented validation and normalization methods for both advisory AI and API lifecycle options to ensure proper configuration.
- Created AuthorityNotificationsOptions and its related classes for managing notification settings, including ack tokens, webhooks, and escalation options.
- Developed IssuerDirectoryClient and related models for interacting with the issuer directory service, including caching mechanisms and HTTP client configurations.
- Added support for dependency injection through ServiceCollectionExtensions for the Issuer Directory Client.
- Updated project file to include necessary package references for the new Issuer Directory Client library.

src/Scanner/__Libraries/StellaOps.Scanner.Surface.Validation/SurfaceValidationSeverity.cs

@@ -0,0 +1,11 @@
+namespace StellaOps.Scanner.Surface.Validation;
+
+/// <summary>
+/// Severity classification for surface validation issues.
+/// </summary>
+public enum SurfaceValidationSeverity
+{
+    Info = 0,
+    Warning = 1,
+    Error = 2,
+}