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.ConfigurationDatabase/Configurations/DeploymentConfiguration.cs

@@ -41,6 +41,33 @@ public class DeploymentRecordConfiguration : IEntityTypeConfiguration<Deployment
     }
 }
 
+public class DeployedConfigSnapshotConfiguration : IEntityTypeConfiguration<DeployedConfigSnapshot>
+{
+    public void Configure(EntityTypeBuilder<DeployedConfigSnapshot> builder)
+    {
+        builder.HasKey(s => s.Id);
+
+        builder.Property(s => s.DeploymentId)
+            .IsRequired()
+            .HasMaxLength(100);
+
+        builder.Property(s => s.RevisionHash)
+            .IsRequired()
+            .HasMaxLength(100);
+
+        builder.Property(s => s.ConfigurationJson)
+            .IsRequired();
+
+        builder.HasOne<Instance>()
+            .WithMany()
+            .HasForeignKey(s => s.InstanceId)
+            .OnDelete(DeleteBehavior.Cascade);
+
+        builder.HasIndex(s => s.InstanceId).IsUnique();
+        builder.HasIndex(s => s.DeploymentId);
+    }
+}
+
 public class SystemArtifactDeploymentRecordConfiguration : IEntityTypeConfiguration<SystemArtifactDeploymentRecord>
 {
     public void Configure(EntityTypeBuilder<SystemArtifactDeploymentRecord> builder)

src/ScadaLink.ConfigurationDatabase/Repositories/DeploymentManagerRepository.cs

@@ -1,5 +1,6 @@
 using Microsoft.EntityFrameworkCore;
 using ScadaLink.Commons.Entities.Deployment;
+using ScadaLink.Commons.Entities.Instances;
 using ScadaLink.Commons.Interfaces.Repositories;
 
 namespace ScadaLink.ConfigurationDatabase.Repositories;
@@ -133,6 +134,59 @@ public class DeploymentManagerRepository : IDeploymentManagerRepository
         return Task.CompletedTask;
     }
 
+    // --- WP-8: DeployedConfigSnapshot ---
+
+    public async Task<DeployedConfigSnapshot?> GetDeployedSnapshotByInstanceIdAsync(int instanceId, CancellationToken cancellationToken = default)
+    {
+        return await _dbContext.Set<DeployedConfigSnapshot>()
+            .FirstOrDefaultAsync(s => s.InstanceId == instanceId, cancellationToken);
+    }
+
+    public async Task AddDeployedSnapshotAsync(DeployedConfigSnapshot snapshot, CancellationToken cancellationToken = default)
+    {
+        await _dbContext.Set<DeployedConfigSnapshot>().AddAsync(snapshot, cancellationToken);
+    }
+
+    public Task UpdateDeployedSnapshotAsync(DeployedConfigSnapshot snapshot, CancellationToken cancellationToken = default)
+    {
+        _dbContext.Set<DeployedConfigSnapshot>().Update(snapshot);
+        return Task.CompletedTask;
+    }
+
+    public async Task DeleteDeployedSnapshotAsync(int instanceId, CancellationToken cancellationToken = default)
+    {
+        var snapshot = await _dbContext.Set<DeployedConfigSnapshot>()
+            .FirstOrDefaultAsync(s => s.InstanceId == instanceId, cancellationToken);
+        if (snapshot != null)
+        {
+            _dbContext.Set<DeployedConfigSnapshot>().Remove(snapshot);
+        }
+    }
+
+    // --- Instance lookups for deployment pipeline ---
+
+    public async Task<Instance?> GetInstanceByIdAsync(int instanceId, CancellationToken cancellationToken = default)
+    {
+        return await _dbContext.Set<Instance>()
+            .Include(i => i.AttributeOverrides)
+            .Include(i => i.ConnectionBindings)
+            .FirstOrDefaultAsync(i => i.Id == instanceId, cancellationToken);
+    }
+
+    public async Task<Instance?> GetInstanceByUniqueNameAsync(string uniqueName, CancellationToken cancellationToken = default)
+    {
+        return await _dbContext.Set<Instance>()
+            .Include(i => i.AttributeOverrides)
+            .Include(i => i.ConnectionBindings)
+            .FirstOrDefaultAsync(i => i.UniqueName == uniqueName, cancellationToken);
+    }
+
+    public Task UpdateInstanceAsync(Instance instance, CancellationToken cancellationToken = default)
+    {
+        _dbContext.Set<Instance>().Update(instance);
+        return Task.CompletedTask;
+    }
+
     public async Task<int> SaveChangesAsync(CancellationToken cancellationToken = default)
     {
         return await _dbContext.SaveChangesAsync(cancellationToken);

src/ScadaLink.ConfigurationDatabase/ScadaLinkDbContext.cs

@@ -40,6 +40,7 @@ public class ScadaLinkDbContext : DbContext, IDataProtectionKeyContext
     // Deployment
     public DbSet<DeploymentRecord> DeploymentRecords => Set<DeploymentRecord>();
     public DbSet<SystemArtifactDeploymentRecord> SystemArtifactDeploymentRecords => Set<SystemArtifactDeploymentRecord>();
+    public DbSet<DeployedConfigSnapshot> DeployedConfigSnapshots => Set<DeployedConfigSnapshot>();
 
     // External Systems
     public DbSet<ExternalSystemDefinition> ExternalSystemDefinitions => Set<ExternalSystemDefinition>();