Phase 3C: Deployment pipeline & Store-and-Forward engine

Deployment Manager (WP-1–8, WP-16):
- DeploymentService: full pipeline (flatten→validate→send→track→audit)
- OperationLockManager: per-instance concurrency control
- StateTransitionValidator: Enabled/Disabled/NotDeployed transition matrix
- ArtifactDeploymentService: broadcast to all sites with per-site results
- Deployment identity (GUID + revision hash), idempotency, staleness detection
- Instance lifecycle commands (disable/enable/delete) with deduplication

Store-and-Forward (WP-9–15):
- StoreAndForwardStorage: SQLite persistence, 3 categories, no max buffer
- StoreAndForwardService: fixed-interval retry, transient-only buffering, parking
- ReplicationService: async best-effort to standby (fire-and-forget)
- Parked message management (query/retry/discard from central)
- Messages survive instance deletion, S&F drains on disable

620 tests pass (+79 new), zero warnings.

src/ScadaLink.Commons/Interfaces/Repositories/IDeploymentManagerRepository.cs

@@ -1,4 +1,5 @@
 using ScadaLink.Commons.Entities.Deployment;
+using ScadaLink.Commons.Entities.Instances;
 using ScadaLink.Commons.Types.Enums;
 
 namespace ScadaLink.Commons.Interfaces.Repositories;
@@ -22,5 +23,16 @@ public interface IDeploymentManagerRepository
     Task UpdateSystemArtifactDeploymentAsync(SystemArtifactDeploymentRecord record, CancellationToken cancellationToken = default);
     Task DeleteSystemArtifactDeploymentAsync(int id, CancellationToken cancellationToken = default);
 
+    // WP-8: DeployedConfigSnapshot
+    Task<DeployedConfigSnapshot?> GetDeployedSnapshotByInstanceIdAsync(int instanceId, CancellationToken cancellationToken = default);
+    Task AddDeployedSnapshotAsync(DeployedConfigSnapshot snapshot, CancellationToken cancellationToken = default);
+    Task UpdateDeployedSnapshotAsync(DeployedConfigSnapshot snapshot, CancellationToken cancellationToken = default);
+    Task DeleteDeployedSnapshotAsync(int instanceId, CancellationToken cancellationToken = default);
+
+    // Instance lookups for deployment pipeline
+    Task<Instance?> GetInstanceByIdAsync(int instanceId, CancellationToken cancellationToken = default);
+    Task<Instance?> GetInstanceByUniqueNameAsync(string uniqueName, CancellationToken cancellationToken = default);
+    Task UpdateInstanceAsync(Instance instance, CancellationToken cancellationToken = default);
+
     Task<int> SaveChangesAsync(CancellationToken cancellationToken = default);
 }