Add new features and tests for AirGap and Time modules

- Introduced `SbomService` tasks documentation.
- Updated `StellaOps.sln` to include new projects: `StellaOps.AirGap.Time` and `StellaOps.AirGap.Importer`.
- Added unit tests for `BundleImportPlanner`, `DsseVerifier`, `ImportValidator`, and other components in the `StellaOps.AirGap.Importer.Tests` namespace.
- Implemented `InMemoryBundleRepositories` for testing bundle catalog and item repositories.
- Created `MerkleRootCalculator`, `RootRotationPolicy`, and `TufMetadataValidator` tests.
- Developed `StalenessCalculator` and `TimeAnchorLoader` tests in the `StellaOps.AirGap.Time.Tests` namespace.
- Added `fetch-sbomservice-deps.sh` script for offline dependency fetching.

src/Findings/StellaOps.Findings.Ledger.WebService/Program.cs

@@ -275,29 +275,7 @@ app.MapGet("/ledger/export/findings", async Task<Results<FileStreamHttpResult, J
         return TypedResults.Problem(statusCode: StatusCodes.Status400BadRequest, title: "page_token_filters_mismatch");
     }
 
-    if (!string.IsNullOrEmpty(page.NextPageToken))
-    {
-        httpContext.Response.Headers["X-Stella-Next-Page-Token"] = page.NextPageToken;
-    }
-    httpContext.Response.Headers["X-Stella-Result-Count"] = page.Items.Count.ToString();
-
-    var acceptsNdjson = httpContext.Request.Headers.Accept.Any(h => h.Contains("application/x-ndjson", StringComparison.OrdinalIgnoreCase));
-    if (acceptsNdjson)
-    {
-        httpContext.Response.ContentType = "application/x-ndjson";
-        var stream = new MemoryStream();
-        await using var writer = new Utf8JsonWriter(stream, new JsonWriterOptions { SkipValidation = false, Indented = false });
-        foreach (var item in page.Items)
-        {
-            JsonSerializer.Serialize(writer, item);
-            writer.Flush();
-            await stream.WriteAsync(new byte[] { (byte)'\n' }, cancellationToken).ConfigureAwait(false);
-        }
-        stream.Position = 0;
-        return TypedResults.Stream(stream, contentType: "application/x-ndjson");
-    }
-
-    return TypedResults.Json(page);
+    return await WritePagedResponse(httpContext, page, cancellationToken).ConfigureAwait(false);
 })
 .WithName("LedgerExportFindings")
 .RequireAuthorization(LedgerExportPolicy)
@@ -342,3 +320,33 @@ static LedgerEventResponse CreateResponse(LedgerEventRecord record, string statu
         MerkleLeafHash = record.MerkleLeafHash,
         RecordedAt = record.RecordedAt
     };
+
+static async Task<Results<FileStreamHttpResult, JsonHttpResult<ExportPage<T>>, ProblemHttpResult>> WritePagedResponse<T>(
+    HttpContext httpContext,
+    ExportPage<T> page,
+    CancellationToken cancellationToken)
+{
+    if (!string.IsNullOrEmpty(page.NextPageToken))
+    {
+        httpContext.Response.Headers["X-Stella-Next-Page-Token"] = page.NextPageToken;
+    }
+    httpContext.Response.Headers["X-Stella-Result-Count"] = page.Items.Count.ToString();
+
+    var acceptsNdjson = httpContext.Request.Headers.Accept.Any(h => h.Contains("application/x-ndjson", StringComparison.OrdinalIgnoreCase));
+    if (acceptsNdjson)
+    {
+        httpContext.Response.ContentType = "application/x-ndjson";
+        var stream = new MemoryStream();
+        await using var writer = new Utf8JsonWriter(stream, new JsonWriterOptions { SkipValidation = false, Indented = false });
+        foreach (var item in page.Items)
+        {
+            JsonSerializer.Serialize(writer, item);
+            writer.Flush();
+            await stream.WriteAsync(new byte[] { (byte)'\n' }, cancellationToken).ConfigureAwait(false);
+        }
+        stream.Position = 0;
+        return TypedResults.Stream(stream, contentType: "application/x-ndjson");
+    }
+
+    return TypedResults.Json(page);
+}