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/CallGraph/IInternalCallGraphBuilder.cs

@@ -0,0 +1,124 @@
+// -----------------------------------------------------------------------------
+// IInternalCallGraphBuilder.cs
+// Sprint: SPRINT_3700_0003_0001_trigger_extraction
+// Description: Interface for building internal call graphs from package sources.
+// -----------------------------------------------------------------------------
+
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace StellaOps.Scanner.VulnSurfaces.CallGraph;
+
+/// <summary>
+/// Builds internal call graphs from package/assembly sources.
+/// Implementations exist for different ecosystems (.NET, Java, Node.js, Python).
+/// </summary>
+public interface IInternalCallGraphBuilder
+{
+    /// <summary>
+    /// Ecosystem this builder supports (e.g., "nuget", "maven", "npm", "pypi").
+    /// </summary>
+    string Ecosystem { get; }
+
+    /// <summary>
+    /// Checks if this builder can handle the given package.
+    /// </summary>
+    /// <param name="packagePath">Path to package archive or extracted directory.</param>
+    bool CanHandle(string packagePath);
+
+    /// <summary>
+    /// Builds an internal call graph from a package.
+    /// </summary>
+    /// <param name="request">Build request with package details.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>Internal call graph for the package.</returns>
+    Task<InternalCallGraphBuildResult> BuildAsync(
+        InternalCallGraphBuildRequest request,
+        CancellationToken cancellationToken = default);
+}
+
+/// <summary>
+/// Request to build an internal call graph.
+/// </summary>
+public sealed record InternalCallGraphBuildRequest
+{
+    /// <summary>
+    /// Package identifier (PURL or package name).
+    /// </summary>
+    public required string PackageId { get; init; }
+
+    /// <summary>
+    /// Package version.
+    /// </summary>
+    public required string Version { get; init; }
+
+    /// <summary>
+    /// Path to the package archive or extracted directory.
+    /// </summary>
+    public required string PackagePath { get; init; }
+
+    /// <summary>
+    /// Whether to include private methods in the graph.
+    /// Default is false (only public API surface).
+    /// </summary>
+    public bool IncludePrivateMethods { get; init; }
+
+    /// <summary>
+    /// Maximum depth for call graph traversal.
+    /// </summary>
+    public int MaxDepth { get; init; } = 20;
+}
+
+/// <summary>
+/// Result of building an internal call graph.
+/// </summary>
+public sealed record InternalCallGraphBuildResult
+{
+    /// <summary>
+    /// Whether the build succeeded.
+    /// </summary>
+    public bool Success { get; init; }
+
+    /// <summary>
+    /// The built call graph (null if failed).
+    /// </summary>
+    public InternalCallGraph? Graph { get; init; }
+
+    /// <summary>
+    /// Error message if build failed.
+    /// </summary>
+    public string? Error { get; init; }
+
+    /// <summary>
+    /// Build duration.
+    /// </summary>
+    public TimeSpan Duration { get; init; }
+
+    /// <summary>
+    /// Number of assemblies/files processed.
+    /// </summary>
+    public int FilesProcessed { get; init; }
+
+    /// <summary>
+    /// Creates a successful result.
+    /// </summary>
+    public static InternalCallGraphBuildResult Ok(InternalCallGraph graph, TimeSpan duration, int filesProcessed) =>
+        new()
+        {
+            Success = true,
+            Graph = graph,
+            Duration = duration,
+            FilesProcessed = filesProcessed
+        };
+
+    /// <summary>
+    /// Creates a failed result.
+    /// </summary>
+    public static InternalCallGraphBuildResult Fail(string error, TimeSpan duration) =>
+        new()
+        {
+            Success = false,
+            Error = error,
+            Duration = duration
+        };
+}