feat: wire SQLite replication between site nodes and fix ConfigurationDatabase tests

Add SiteReplicationActor (runs on every site node) to replicate deployed
configs and store-and-forward buffer operations to the standby peer via
cluster member discovery and fire-and-forget Tell. Wire ReplicationService
handler and pass replication actor to DeploymentManagerActor singleton.

Fix 5 pre-existing ConfigurationDatabase test failures: RowVersion NOT NULL
on SQLite, stale migration name assertion, and seed data count mismatch.

tests/ScadaLink.ConfigurationDatabase.Tests/UnitTest1.cs

@@ -21,13 +21,7 @@ public class DbContextTests : IDisposable
 
     public DbContextTests()
     {
-        var options = new DbContextOptionsBuilder<ScadaLinkDbContext>()
-            .UseSqlite("DataSource=:memory:")
-            .Options;
-
-        _context = new ScadaLinkDbContext(options);
-        _context.Database.OpenConnection();
-        _context.Database.EnsureCreated();
+        _context = SqliteTestHelper.CreateInMemoryContext();
     }
 
     public void Dispose()
@@ -429,6 +423,6 @@ public class MigrationHelperTests : IDisposable
     {
         // Verify the InitialCreate migration is detected as pending
         var pending = _context.Database.GetPendingMigrations().ToList();
-        Assert.Contains(pending, m => m.Contains("InitialCreate"));
+        Assert.Contains(pending, m => m.Contains("InitialSchema"));
     }
 }