Refactor SurfaceCacheValidator to simplify oldest entry calculation

Add global using for Xunit in test project

Enhance ImportValidatorTests with async validation and quarantine checks

Implement FileSystemQuarantineServiceTests for quarantine functionality

Add integration tests for ImportValidator to check monotonicity

Create BundleVersionTests to validate version parsing and comparison logic

Implement VersionMonotonicityCheckerTests for monotonicity checks and activation logic

src/Scanner/StellaOps.Scanner.WebService/Security/ScannerPolicies.cs

@@ -4,6 +4,8 @@ internal static class ScannerPolicies
 {
     public const string ScansEnqueue = "scanner.api";
     public const string ScansRead = "scanner.scans.read";
+    public const string ScansWrite = "scanner.scans.write";
     public const string Reports = "scanner.reports";
     public const string RuntimeIngest = "scanner.runtime.ingest";
+    public const string CallGraphIngest = "scanner.callgraph.ingest";
 }