feat: add Vite configuration for Tiku.PlatformAdmin.Web and update documentation

- Introduced Vite configuration files (vite.config.js, vite.config.ts, vite.config.d.ts) for the React frontend.
- Configured server proxy settings for API endpoints.
- Added Vitest configuration files (vitest.config.js, vitest.config.ts, vitest.config.d.ts) for testing.
- Updated architecture overview to reflect the separation of the platform admin frontend into its own React project.
- Modified quickstart documentation to guide users on starting the platform admin frontend.

Tiku.IntegrationTests/Api/PlatformAdminFrontendSeparationTests.cs

@@ -0,0 +1,23 @@
+using System.Net;
+
+namespace Tiku.IntegrationTests.Api;
+
+public sealed class PlatformAdminFrontendSeparationTests
+{
+    [Theory]
+    [InlineData("/platform-admin")]
+    [InlineData("/platform-admin/")]
+    [InlineData("/platform-admin/app.js")]
+    public async Task WebApi_does_not_host_platform_admin_frontend(string path)
+    {
+        await using var factory = new ApiTestFactory();
+        using var client = factory.CreateClient(new()
+        {
+            AllowAutoRedirect = false
+        });
+
+        using var response = await client.GetAsync(path);
+
+        Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
+    }
+}