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.

docs/modules/sbomservice/prep/2025-11-20-build-infra-prep.md

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+# Build/Infra Prep — PREP-BUILD-INFRA-SBOM-SERVICE-GUILD-BLOCKED-M
+
+Status: Draft (2025-11-20)
+Owners: SBOM Service Guild
+Scope: Document restore/build blocking issues awaiting vetted feed/cache.
+
+## Blocker summary
+- Multiple restore attempts hang/fail; need vetted NuGet feed/cache for SBOM Service solution.
+
+## Needed actions
+- Provide approved offline feed snapshot for SBOM Service dependencies.
+- CI runner with feed configured to validate restore.
+
+## Handoff
+Use as PREP artefact; update once feed snapshot is supplied and restore passes.

docs/modules/sbomservice/prep/2025-11-20-sbom-service-21-001-prep.md

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+# SBOM Service Prep — PREP-SBOM-SERVICE-21-001
+
+Status: Draft (2025-11-20)
+Owners: SBOM Service Guild · Cartographer Guild
+Scope: Waiting on LNM v1 fixtures to freeze normalized SBOM projection read API.
+
+## Needed inputs
+- LNM v1 fixtures (due 2025-11-18 UTC) for schema alignment.
+
+## Proposed API surface (draft)
+- `GET /sboms/{id}/projection` with query `page`, `page_size`, `tenant_id`.
+- Response includes `components[]`, `licenses[]`, `hashes[]`, `provenance`.
+- Deterministic ordering, tenant enforcement.
+
+## Open decisions
+- Pagination defaults and max page size.
+- Which hash algorithms to expose.
+
+## Handoff
+Use as PREP artefact; finalize once fixtures arrive.