feat(db): add SourceNode column to SiteCalls

src/ScadaLink.ConfigurationDatabase/Configurations/SiteCallEntityTypeConfiguration.cs

@@ -59,10 +59,14 @@ public class SiteCallEntityTypeConfiguration : IEntityTypeConfiguration<SiteCall
         builder.Property(s => s.LastError)
             .HasMaxLength(1024);
 
-        // SourceNode (Audit Log #23, SourceNode-stamping): mapped in a follow-on migration
-        // (AddSiteCallSourceNode). Ignored here for now so the AddAuditLogSourceNode
-        // migration only touches AuditLog. Removed in the AddSiteCallSourceNode commit.
-        builder.Ignore(s => s.SourceNode);
+        // SourceNode (Audit Log #23, SourceNode-stamping): node-local identifier of the
+        // cluster member that produced the call (e.g. "node-a", "central-a"). NULL is
+        // valid for rows that pre-date this feature and for reconciled rows from a
+        // retired node. ASCII — varchar(64). No index — Site Call Audit KPIs are
+        // per-site, not per-node, on this table.
+        builder.Property(s => s.SourceNode)
+            .HasColumnType("varchar(64)")
+            .HasMaxLength(64);
 
         // Indexes — names locked for reconciliation/migration discoverability.
         // Source_Created backs "calls from this site" (Central UI Site Calls page,