Add Catalogs page and simplify dashboard navigation

- Added a new Catalogs.razor page with a CatalogsGrid component and navigation link.
- Simplified Dashboard.razor to only show the default dashboard in designer mode; removed catalog grid options.
- Updated dashboard parameter logic to always redirect to "dashboards/default" unless already selected.

DbFirst.BlazorWebApp/Components/Layout/NavMenu.razor

@@ -25,6 +25,12 @@
                 <span class="bi bi-list-nested-nav-menu" aria-hidden="true"></span> Weather
             </NavLink>
         </div>
+        <div class="nav-item px-3">
+            <NavLink class="nav-link" href="catalogs">
+                <span class="bi bi-collection-nav-menu" aria-hidden="true"></span> Catalogs
+            </NavLink>
+        </div>
+
         <div class="nav-item px-3">
             <NavLink class="nav-link" href="dashboards/default">
                 <span class="oi oi-list-rich" aria-hidden="true"></span> Dashboards