Refactor DTOs, add Blazor WASM frontend, enable CORS

- Split `CatalogDto` into `CatalogReadDto` and `CatalogWriteDto` for clear separation of read/write operations in both backend and frontend.
- Updated API controllers, services, and AutoMapper profiles to use new DTOs; ensured audit fields are set in service layer.
- Enabled CORS in the API project to support Blazor WASM frontend.
- Added new Blazor WebAssembly project (`DbFirst.BlazorWasm`) with catalog management UI, API client, Bootstrap v5.1.0 styling, and configuration-driven API base URL.
- Included `bootstrap.min.css` and its source map for frontend styling and easier debugging.
- Updated solution file to include new project and support multiple build configurations.
- Result: improved API design, clean DTO separation, and a modern interactive frontend for catalog management.

DbFirst.BlazorWasm/Layout/MainLayout.razor

@@ -0,0 +1,16 @@
+@inherits LayoutComponentBase
+<div class="page">
+    <div class="sidebar">
+        <NavMenu />
+    </div>
+
+    <main>
+        <div class="top-row px-4">
+            <a href="https://learn.microsoft.com/aspnet/core/" target="_blank">About</a>
+        </div>
+
+        <article class="content px-4">
+            @Body
+        </article>
+    </main>
+</div>