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/Pages/Companies/CompanyCreate.razor

@@ -0,0 +1,52 @@
+@page "/admin/companies/create"
+@rendermode @(new InteractiveWebAssemblyRenderMode(prerender: false))
+@attribute [Authorize]
+@using TaxBaik.WasmClient.Components.Admin.Forms
+@inject IApiClient ApiClient
+@inject NavigationManager Navigation
+@inject ISnackbar Snackbar
+
+<PageTitle>고객사 등록</PageTitle>
+
+<section class="admin-page-hero">
+    <div>
+        <MudText Typo="Typo.caption" Class="admin-eyebrow">Settings</MudText>
+        <MudText Typo="Typo.h4" Class="admin-page-title">새 고객사 등록</MudText>
+        <MudText Typo="Typo.body2" Class="admin-page-subtitle">새로운 고객사를 추가합니다.</MudText>
+    </div>
+    <MudButton Variant="Variant.Outlined" StartIcon="@Icons.Material.Filled.Close" @onclick="GoBack">취소</MudButton>
+</section>
+
+<MudPaper Class="pa-4 mt-4" Elevation="1">
+    <CompanyForm ButtonText="등록" OnSubmit="HandleCreate" OnCancel="GoBack" />
+</MudPaper>
+
+@code {
+    private void GoBack()
+    {
+        Navigation.NavigateTo("/taxbaik/admin/companies");
+    }
+
+    private async Task HandleCreate(CompanyForm.CompanyFormModel model)
+    {
+        try
+        {
+            await ApiClient.PostAsync<object>("company", new
+            {
+                companyCode = model.CompanyCode,
+                companyName = model.CompanyName,
+                contactPerson = model.ContactPerson,
+                phone = model.Phone,
+                email = model.Email,
+                memo = model.Memo
+            });
+
+            Snackbar.Add("고객사가 등록되었습니다.", Severity.Success);
+            Navigation.NavigateTo("/taxbaik/admin/companies");
+        }
+        catch (Exception ex)
+        {
+            Snackbar.Add($"등록 실패: {ex.Message}", Severity.Error);
+        }
+    }
+}