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.Client/Components/Admin/Shared/AdminMetricCard.razor

@@ -1,36 +0,0 @@
-<div class="admin-metric-card @Accent cursor-pointer" @onclick="OnClick">
-    <div class="admin-metric-card-body">
-        <span class="admin-metric-card-label">@Label</span>
-        <div class="admin-metric-card-value-row">
-            <span class="admin-metric-card-value" style="color: @ValueColor;">@Value</span>
-            <span class="admin-metric-card-icon" style="color: @IconColor;">@Icon</span>
-        </div>
-        <span class="admin-metric-card-caption">@Caption</span>
-    </div>
-</div>
-
-@code {
-    [Parameter, EditorRequired]
-    public string Label { get; set; } = "";
-
-    [Parameter, EditorRequired]
-    public object? Value { get; set; }
-
-    [Parameter, EditorRequired]
-    public string Caption { get; set; } = "";
-
-    [Parameter, EditorRequired]
-    public string Accent { get; set; } = "";
-
-    [Parameter, EditorRequired]
-    public string Icon { get; set; } = "";
-
-    [Parameter]
-    public string ValueColor { get; set; } = "inherit";
-
-    [Parameter]
-    public string IconColor { get; set; } = "inherit";
-
-    [Parameter]
-    public EventCallback OnClick { get; set; }
-}