refactor: fully integrate Browser Client into main Web server

BREAKING CHANGE: Removed TaxBaik.Web.Client project (separate WASM app)

Changes:
- Migrated all Blazor components to TaxBaik.Web/Components/Admin
- Migrated all Browser Client services to Components/Admin/Services
- Updated Program.cs to use integrated components (same assembly)
- Removed AddAdditionalAssemblies (no longer needed)
- Updated _Imports.razor with correct namespaces

Architecture:
✅ API-First: REST endpoints in TaxBaik.Web (ASP.NET Core)
✅ Client-Side: Blazor WASM components in TaxBaik.Web/Components
✅ Unified: Both API and UI served from single web server
✅ No separation: No separate client project

Result:
- Single deploy unit (TaxBaik.Web)
- API served only from web server
- Blazor renders client-side (prerender: false for protected pages)
- Monolithic web app architecture

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/TaxBaik.Web/Components/Admin/Shared/AdminDetailSection.razor

@@ -0,0 +1,21 @@
+<MudPaper Class="@CssClass" Elevation="@Elevation">
+    @if (!string.IsNullOrWhiteSpace(Title))
+    {
+        <MudText Typo="Typo.h6" Class="mb-3">@Title</MudText>
+    }
+    @ChildContent
+</MudPaper>
+
+@code {
+    [Parameter]
+    public string? Title { get; set; }
+
+    [Parameter]
+    public RenderFragment? ChildContent { get; set; }
+
+    [Parameter]
+    public string CssClass { get; set; } = "pa-4";
+
+    [Parameter]
+    public int Elevation { get; set; } = 1;
+}