docs: backfill XML documentation across 756 files

Adds <summary>, <param>, <typeparam>, and <inheritdoc/> tags to public
members surfaced by commentchecker — resolves 5,847 of 5,869 issues
(99.6%) across three /fixdocs passes.

src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/Services/JsonSettingsService.cs

@@ -19,6 +19,8 @@ public sealed class JsonSettingsService : ISettingsService
         WriteIndented = true
     };
 
+    /// <summary>Loads user settings from the settings file.</summary>
+    /// <returns>The loaded user settings, or a new default instance if load fails.</returns>
     public UserSettings Load()
     {
         try
@@ -35,6 +37,8 @@ public sealed class JsonSettingsService : ISettingsService
         }
     }
 
+    /// <summary>Saves user settings to the settings file.</summary>
+    /// <param name="settings">The user settings to save.</param>
     public void Save(UserSettings settings)
     {
         try