feat(deploy): surface connection-level changes in the deployment diff (#10)

ComputeConnectionsDiff existed with tests but was never called and ConfigurationDiff
had no slot for it, so standalone connection endpoint/protocol/failover drift never
appeared in the deployment diff (only per-attribute binding drift did). Add a
ConnectionChanges slot, wire ComputeConnectionsDiff into ComputeDiff, and render the
connection section in the deployment diff UI.

src/ZB.MOM.WW.ScadaBridge.TemplateEngine/Flattening/DiffService.cs

@@ -42,6 +42,13 @@ public class DiffService
             s => s.CanonicalName,
             ScriptsEqual);
 
+        // TemplateEngine-018: surface standalone connection endpoint/protocol/
+        // failover drift. Per-attribute binding changes already show up under
+        // AttributeChanges, but a connection's own ConfigurationJson /
+        // BackupConfigurationJson / Protocol / FailoverRetryCount edits do not —
+        // those only appear here.
+        var connectionChanges = ComputeConnectionsDiff(oldConfig, newConfig);
+
         return new ConfigurationDiff
         {
             InstanceUniqueName = newConfig.InstanceUniqueName,
@@ -49,7 +56,8 @@ public class DiffService
             NewRevisionHash = newRevisionHash,
             AttributeChanges = attributeChanges,
             AlarmChanges = alarmChanges,
-            ScriptChanges = scriptChanges
+            ScriptChanges = scriptChanges,
+            ConnectionChanges = connectionChanges
         };
     }
 
@@ -159,11 +167,10 @@ public class DiffService
     /// TemplateEngine-018: produces a per-connection diff between two flattened
     /// configurations, emitting Added / Removed / Changed entries keyed by the
     /// connection name. Mirrors the existing <see cref="ComputeEntityDiff{T}"/>
-    /// shape used for attributes / alarms / scripts but is exposed as a separate
-    /// method because <see cref="ConfigurationDiff"/> in
-    /// <c>ZB.MOM.WW.ScadaBridge.Commons</c> does not yet carry a <c>ConnectionChanges</c>
-    /// slot — the public diff record will be extended in a paired Commons change
-    /// (this file is the only one in this fix's scope). A null
+    /// shape used for attributes / alarms / scripts. Called by
+    /// <see cref="ComputeDiff"/> to populate
+    /// <see cref="ConfigurationDiff.ConnectionChanges"/>, and exposed publicly so
+    /// callers can compute connection drift in isolation. A null
     /// <c>Connections</c> dictionary on either side is treated as the empty map.
     /// </summary>
     /// <param name="oldConfig">The previously deployed configuration, or null