docs+ui: backfill XML doc comments and finish dashboard layout pass

Adds missing <summary>/<param> XML docs across 99 server, worker, and test
files so CommentChecker reports zero issues (TreatWarningsAsErrors needs the
analyzer clean). Bundles in WIP dashboard work: NavSection extraction,
MainLayout/site.css/js styling alignment, and DashboardOptions/Auth tweaks.

src/ZB.MOM.WW.MxGateway.Server/Security/Authentication/ApiKeyConstraintSerializer.cs

@@ -10,12 +10,16 @@ public static class ApiKeyConstraintSerializer
         WriteIndented = false,
     };
 
+    /// <summary>Serializes API key constraints to JSON, or returns null if the constraints are empty.</summary>
+    /// <param name="constraints">The constraints to serialize.</param>
     public static string? Serialize(ApiKeyConstraints constraints)
     {
         ArgumentNullException.ThrowIfNull(constraints);
         return constraints.IsEmpty ? null : JsonSerializer.Serialize(constraints, JsonOptions);
     }
 
+    /// <summary>Deserializes API key constraints from JSON, or returns empty constraints if JSON is null or whitespace.</summary>
+    /// <param name="json">The JSON string to deserialize.</param>
     public static ApiKeyConstraints Deserialize(string? json)
     {
         if (string.IsNullOrWhiteSpace(json))