refactor: complete WebAssembly migration - proper architecture

Phase 8: Complete WebAssembly 렌더 모드 전환 (정공법)

Migration Summary:
- ALL Admin components → TaxBaik.Web.Client
- Routes.razor, Pages/*, Layout/*, Shared/*, Forms/*
- App.razor → TaxBaik.WasmClient (호스트 컴포넌트)
- Shared utilities → TaxBaik.Application.Utils

Architecture:
✅ App.razor: TaxBaik.WasmClient (WebAssembly, 호스트)
✅ Routes + Pages: TaxBaik.WasmClient (WebAssembly)
✅ Layout + Shared + Forms: TaxBaik.WasmClient (WebAssembly)
✅ Services: TaxBaik.Web (API-First)

Key Changes:
- Namespaces: TaxBaik.Web.Components.Admin → TaxBaik.WasmClient.Components.Admin
- Shared utilities: TaxBaik.Application.Utils (single source of truth)
- Program.cs: MapRazorComponents<TaxBaik.WasmClient.Components.Admin.App>()
- _Imports.razor: Components/Admin 폴더에 재구성

Build Status: ✅ 0 errors, 0 warnings

Benefits:
- Stateless server (no Circuit memory)
- Client-side rendering (WebAssembly)
- Unlimited concurrent users (horizontal scaling)
- ERP-ready architecture

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

TaxBaik.Web.Client/Components/Admin/Shared/AdminFormActions.razor

@@ -0,0 +1,44 @@
+<div class="d-flex gap-2">
+    <MudButton Variant="@SubmitVariant"
+               Color="@SubmitColor"
+               StartIcon="@SubmitIcon"
+               @onclick="OnSubmit"
+               Disabled="@IsSubmitting">
+        @(IsSubmitting ? LoadingText : SubmitText)
+    </MudButton>
+    @if (OnCancel.HasDelegate)
+    {
+        <MudButton Variant="Variant.Outlined" @onclick="OnCancel">
+            @CancelText
+        </MudButton>
+    }
+</div>
+
+@code {
+    [Parameter, EditorRequired]
+    public string SubmitText { get; set; } = "저장";
+
+    [Parameter]
+    public string LoadingText { get; set; } = "저장 중...";
+
+    [Parameter]
+    public string CancelText { get; set; } = "취소";
+
+    [Parameter]
+    public Variant SubmitVariant { get; set; } = Variant.Filled;
+
+    [Parameter]
+    public Color SubmitColor { get; set; } = Color.Primary;
+
+    [Parameter]
+    public string? SubmitIcon { get; set; }
+
+    [Parameter]
+    public EventCallback OnSubmit { get; set; }
+
+    [Parameter]
+    public EventCallback OnCancel { get; set; }
+
+    [Parameter]
+    public bool IsSubmitting { get; set; }
+}