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/_Imports.razor

@@ -0,0 +1,17 @@
+@using System.Net.Http
+@using System.Net.Http.Json
+@using Microsoft.AspNetCore.Authorization
+@using Microsoft.AspNetCore.Components.Authorization
+@using Microsoft.AspNetCore.Components.Forms
+@using Microsoft.AspNetCore.Components.Routing
+@using Microsoft.AspNetCore.Components.Web
+@using Microsoft.AspNetCore.Components.Web.Virtualization
+@using Microsoft.AspNetCore.Components.WebAssembly.Http
+@using Microsoft.JSInterop
+@using MudBlazor
+@using TaxBaik.Web.Components.Admin
+@using TaxBaik.Web.Components.Admin.Services
+@using TaxBaik.Web.Components.Admin.Services.AdminClients
+@using TaxBaik.Application.DTOs
+@using TaxBaik.Domain.Entities
+@using static Microsoft.AspNetCore.Components.Web.RenderMode