semi implemented and features implemented save checkpoint

docs/features/unchecked/attestor/enhanced-rekor-proof-persistence.md

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+# Enhanced Rekor Proof Persistence
+
+## Module
+Attestor
+
+## Status
+IMPLEMENTED
+
+## Description
+Enhanced Rekor proof persistence storing checkpoint signatures, checkpoint notes, entry body hashes, and verification timestamps for complete offline verification without Rekor connectivity.
+
+## Implementation Details
+- **Rekor Entry Entity**: `src/Attestor/__Libraries/StellaOps.Attestor.Persistence/Entities/RekorEntryEntity.cs` -- database entity storing Rekor entries with inclusion proofs, checkpoint data, and verification timestamps.
+- **DSSE Envelope Entity**: `Entities/DsseEnvelopeEntity.cs` -- persists signed DSSE envelopes associated with Rekor entries.
+- **Spine Entity**: `Entities/SpineEntity.cs` -- persists proof spine data.
+- **Trust Anchor Entity**: `Entities/TrustAnchorEntity.cs` -- stores trust anchor data for offline verification.
+- **Proof Chain DB Context**: `ProofChainDbContext.cs` -- EF Core DbContext for proof chain persistence.
+- **Repositories**: `Repositories/IProofChainRepository.cs` -- repository interface. `IVerdictLedgerRepository.cs` -- verdict ledger repository.
+- **Trust Anchor Matcher**: `Services/TrustAnchorMatcher.cs` -- matches entries against persisted trust anchors.
+- **Rekor Checkpoint Store**: `src/Attestor/StellaOps.Attestor/StellaOps.Attestor.Storage/Rekor/PostgresRekorCheckpointStore.cs` -- PostgreSQL checkpoint persistence.
+- **Offline Receipt Verifier**: `StellaOps.Attestor.Core/Verification/RekorOfflineReceiptVerifier.cs` -- verifies receipts using persisted data.
+- **Tests**: `__Tests/StellaOps.Attestor.Persistence.Tests/ProofChainDbContextTests.cs`, `TrustAnchorMatcherTests.cs`
+
+## E2E Test Plan
+- [ ] Persist a Rekor entry with inclusion proof and checkpoint via `RekorEntryEntity` and retrieve it, verifying all fields
+- [ ] Persist a DSSE envelope via `DsseEnvelopeEntity` and verify association with its Rekor entry
+- [ ] Store a trust anchor via `TrustAnchorEntity` and verify `TrustAnchorMatcher` can match entries against it
+- [ ] Store checkpoint signatures via `PostgresRekorCheckpointStore` and retrieve them for offline verification
+- [ ] Verify a Rekor receipt offline using `RekorOfflineReceiptVerifier` with only persisted data (no network)
+- [ ] Persist a spine entity and verify it links to its constituent proof entries
+- [ ] Verify `ProofChainDbContext` migrations create correct schema with all required tables and indexes