Refactor dashboard navigation, catalog grid, and API client

- Add sidebar dashboard navigation and support multiple dashboards
- Extract catalog grid/form logic to reusable CatalogsGrid component
- Add CatalogApiClient and DTOs for catalog CRUD operations
- Define dashboards with JSON data sources (Default, CatalogsGrid)
- Update configuration for dashboard and API endpoints
- Improve styling and imports for modularity and maintainability

DbFirst.BlazorWebApp/Models/CatalogReadDto.cs

@@ -0,0 +1,12 @@
+namespace DbFirst.BlazorWebApp.Models;
+
+public class CatalogReadDto
+{
+    public int Guid { get; set; }
+    public string CatTitle { get; set; } = null!;
+    public string CatString { get; set; } = null!;
+    public string AddedWho { get; set; } = null!;
+    public DateTime AddedWhen { get; set; }
+    public string? ChangedWho { get; set; }
+    public DateTime? ChangedWhen { get; set; }
+}