feat(telemetry): add telemetry client and services for tracking events

- Implemented TelemetryClient to handle event queuing and flushing to the telemetry endpoint.
- Created TtfsTelemetryService for emitting specific telemetry events related to TTFS.
- Added tests for TelemetryClient to ensure event queuing and flushing functionality.
- Introduced models for reachability drift detection, including DriftResult and DriftedSink.
- Developed DriftApiService for interacting with the drift detection API.
- Updated FirstSignalCardComponent to emit telemetry events on signal appearance.
- Enhanced localization support for first signal component with i18n strings.

src/Scanner/__Libraries/StellaOps.Scanner.VulnSurfaces.Tests/InternalCallGraphTests.cs

@@ -0,0 +1,133 @@
+// -----------------------------------------------------------------------------
+// InternalCallGraphTests.cs
+// Sprint: SPRINT_3700_0003_0001_trigger_extraction
+// Description: Unit tests for InternalCallGraph.
+// -----------------------------------------------------------------------------
+
+using StellaOps.Scanner.VulnSurfaces.CallGraph;
+using StellaOps.Scanner.VulnSurfaces.Models;
+using Xunit;
+
+namespace StellaOps.Scanner.VulnSurfaces.Tests;
+
+public class InternalCallGraphTests
+{
+    [Fact]
+    public void AddMethod_StoresMethod()
+    {
+        // Arrange
+        var graph = new InternalCallGraph
+        {
+            PackageId = "TestPackage",
+            Version = "1.0.0"
+        };
+
+        var method = new InternalMethodRef
+        {
+            MethodKey = "Namespace.Class::Method()",
+            Name = "Method",
+            DeclaringType = "Namespace.Class",
+            IsPublic = true
+        };
+
+        // Act
+        graph.AddMethod(method);
+
+        // Assert
+        Assert.True(graph.ContainsMethod("Namespace.Class::Method()"));
+        Assert.Equal(1, graph.MethodCount);
+    }
+
+    [Fact]
+    public void AddEdge_CreatesForwardAndReverseMapping()
+    {
+        // Arrange
+        var graph = new InternalCallGraph
+        {
+            PackageId = "TestPackage",
+            Version = "1.0.0"
+        };
+
+        var edge = new InternalCallEdge
+        {
+            Caller = "A::M1()",
+            Callee = "A::M2()"
+        };
+
+        // Act
+        graph.AddEdge(edge);
+
+        // Assert
+        Assert.Contains("A::M2()", graph.GetCallees("A::M1()"));
+        Assert.Contains("A::M1()", graph.GetCallers("A::M2()"));
+        Assert.Equal(1, graph.EdgeCount);
+    }
+
+    [Fact]
+    public void GetPublicMethods_ReturnsOnlyPublic()
+    {
+        // Arrange
+        var graph = new InternalCallGraph
+        {
+            PackageId = "TestPackage",
+            Version = "1.0.0"
+        };
+
+        graph.AddMethod(new InternalMethodRef
+        {
+            MethodKey = "A::Public()",
+            Name = "Public",
+            DeclaringType = "A",
+            IsPublic = true
+        });
+
+        graph.AddMethod(new InternalMethodRef
+        {
+            MethodKey = "A::Private()",
+            Name = "Private",
+            DeclaringType = "A",
+            IsPublic = false
+        });
+
+        // Act
+        var publicMethods = graph.GetPublicMethods().ToList();
+
+        // Assert
+        Assert.Single(publicMethods);
+        Assert.Equal("A::Public()", publicMethods[0].MethodKey);
+    }
+
+    [Fact]
+    public void GetCallees_EmptyForUnknownMethod()
+    {
+        // Arrange
+        var graph = new InternalCallGraph
+        {
+            PackageId = "TestPackage",
+            Version = "1.0.0"
+        };
+
+        // Act
+        var callees = graph.GetCallees("Unknown::Method()");
+
+        // Assert
+        Assert.Empty(callees);
+    }
+
+    [Fact]
+    public void GetMethod_ReturnsNullForUnknown()
+    {
+        // Arrange
+        var graph = new InternalCallGraph
+        {
+            PackageId = "TestPackage",
+            Version = "1.0.0"
+        };
+
+        // Act
+        var method = graph.GetMethod("Unknown::Method()");
+
+        // Assert
+        Assert.Null(method);
+    }
+}