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.

tests/AirGap/StellaOps.AirGap.Time.Tests/TimeTokenParserTests.cs

@@ -0,0 +1,34 @@
+using StellaOps.AirGap.Time.Models;
+using StellaOps.AirGap.Time.Parsing;
+
+namespace StellaOps.AirGap.Time.Tests;
+
+public class TimeTokenParserTests
+{
+    [Fact]
+    public void EmptyTokenFails()
+    {
+        var parser = new TimeTokenParser();
+        var result = parser.TryParse(Array.Empty<byte>(), TimeTokenFormat.Roughtime, out var anchor);
+
+        Assert.False(result.IsValid);
+        Assert.Equal("token-empty", result.Reason);
+        Assert.Equal(TimeAnchor.Unknown, anchor);
+    }
+
+    [Fact]
+    public void RoughtimeTokenProducesDigest()
+    {
+        var parser = new TimeTokenParser();
+        var token = new byte[] { 0x01, 0x02, 0x03 };
+
+        var result = parser.TryParse(token, TimeTokenFormat.Roughtime, out var anchor);
+
+        Assert.True(result.IsValid);
+        Assert.Equal("Roughtime", anchor.Format);
+        Assert.Equal("roughtime-token", anchor.Source);
+        Assert.Equal("structure-stubbed", result.Reason);
+        Assert.Matches("^[0-9a-f]{64}$", anchor.TokenDigest);
+        Assert.NotEqual(DateTimeOffset.UnixEpoch, anchor.AnchorTime); // deterministic derivation
+    }
+}