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.Tests/Exports/ExportPagingTests.cs

@@ -0,0 +1,51 @@
+using StellaOps.Findings.Ledger.Infrastructure.Exports;
+using Xunit;
+
+namespace StellaOps.Findings.Ledger.Tests.Exports;
+
+public class ExportPagingTests
+{
+    [Fact]
+    public void ComputeFiltersHash_IsDeterministic()
+    {
+        var left = new Dictionary<string, string?>
+        {
+            ["shape"] = "canonical",
+            ["since_sequence"] = "10",
+            ["until_sequence"] = "20"
+        };
+
+        var right = new Dictionary<string, string?>
+        {
+            ["until_sequence"] = "20",
+            ["shape"] = "canonical",
+            ["since_sequence"] = "10"
+        };
+
+        var leftHash = ExportPaging.ComputeFiltersHash(left);
+        var rightHash = ExportPaging.ComputeFiltersHash(right);
+
+        Assert.Equal(leftHash, rightHash);
+    }
+
+    [Fact]
+    public void PageToken_RoundTrips()
+    {
+        var key = new ExportPaging.ExportPageKey(5, "v1", "abc123");
+        var filtersHash = ExportPaging.ComputeFiltersHash(new Dictionary<string, string?>
+        {
+            ["shape"] = "canonical"
+        });
+
+        var token = ExportPaging.CreatePageToken(key, filtersHash);
+
+        var parsed = ExportPaging.TryParsePageToken(token, filtersHash, out var recovered, out var error);
+
+        Assert.True(parsed);
+        Assert.Null(error);
+        Assert.NotNull(recovered);
+        Assert.Equal(key.SequenceNumber, recovered!.SequenceNumber);
+        Assert.Equal(key.PolicyVersion, recovered.PolicyVersion);
+        Assert.Equal(key.CycleHash, recovered.CycleHash);
+    }
+}