Update dashboard navigation and dynamic loading

- Changed NavMenu to link to /dashboards instead of /dashboards/default
- Refactored Dashboard.razor to list dashboards from API
- Dashboard viewer/designer now loads by selected dashboard ID
- Mode toggle preserves selected dashboard and mode
- Added DashboardApiClient and DashboardInfoDto for API integration
- Registered DashboardApiClient for DI and HTTP client setup in Program.cs

DbFirst.BlazorWasm/Program.cs

@@ -17,5 +17,6 @@ builder.Services.AddDevExpressBlazor();
 var apiBaseUrl = builder.Configuration["ApiBaseUrl"] ?? builder.HostEnvironment.BaseAddress;
 builder.Services.AddScoped(sp => new HttpClient { BaseAddress = new Uri(apiBaseUrl) });
 builder.Services.AddScoped<CatalogApiClient>();
+builder.Services.AddScoped<DashboardApiClient>();
 
 await builder.Build().RunAsync();