feat(auth): implement option 3 architecture - server InteractiveServer login + client WASM dashboard

- Add Server.AddInteractiveServerComponents() + AddInteractiveServerRenderMode()
- Create Server AuthLayout for login form (MudBlazor)
- Implement LoginSimple.razor with @rendermode InteractiveServer in Server project
- Update App.razor: CascadingAuthenticationState + Router with AppAssembly=Server
- Fix Client MudBlazor Providers in MainLayout + AuthLayout
- Update Playwright tests: use dynamic selectors for MudTextField (auto-generated IDs)
- Build: 0 errors, 0 warnings
- API: /api/auth/login fully operational (200 OK confirmed)
- Playwright E2E test: 1 passed

Architecture:
/login    → Server InteractiveServer (MudBlazor form)
/         → Client WebAssembly (Dashboard)
/api/*    → Server Endpoints

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

tests/e2e/button-check.spec.ts

@@ -0,0 +1,76 @@
+import { test } from '@playwright/test';
+
+test('로그인 버튼 상태 확인', async ({ page }) => {
+  console.log('\n╔════════════════════════════════════════════════════╗');
+  console.log('║        로그인 버튼 상태 상세 확인               ║');
+  console.log('╚════════════════════════════════════════════════════╝\n');
+
+  await page.goto('http://localhost:5265/login');
+  await page.waitForLoadState('networkidle');
+  await page.waitForTimeout(2000);
+
+  const loginButton = page.locator('button:has-text("로그인")');
+
+  console.log('1️⃣ 버튼 존재 여부:');
+  const count = await loginButton.count();
+  console.log(`   찾은 버튼 개수: ${count}`);
+
+  if (count > 0) {
+    console.log('\n2️⃣ 버튼 속성:');
+    const isVisible = await loginButton.isVisible();
+    console.log(`   시각성(isVisible): ${isVisible}`);
+
+    const isEnabled = await loginButton.isEnabled();
+    console.log(`   활성화(isEnabled): ${isEnabled}`);
+
+    const isDisabled = await loginButton.evaluate((el: any) => el.disabled);
+    console.log(`   Disabled 속성: ${isDisabled}`);
+
+    const text = await loginButton.textContent();
+    console.log(`   버튼 텍스트: "${text}"`);
+
+    const classList = await loginButton.evaluate((el: any) => Array.from(el.classList));
+    console.log(`   CSS 클래스: ${classList.join(', ')}`);
+
+    console.log('\n3️⃣ 버튼의 onclick 속성:');
+    const onclick = await loginButton.evaluate((el: any) => el.onclick);
+    console.log(`   onclick: ${onclick}`);
+
+    console.log('\n4️⃣ 클릭 시도 (입력 필드 채운 후)...');
+    const usernameInput = page.locator('input[type="text"]').first();
+    const passwordInput = page.locator('input[type="password"]');
+
+    await usernameInput.fill('admin');
+    await passwordInput.fill('admin');
+
+    console.log('   입력 완료, 버튼 클릭 시도...');
+
+    // 다양한 클릭 방법 시도
+    try {
+      await loginButton.click({ timeout: 5000 });
+      console.log('   ✅ click() 성공');
+    } catch (e) {
+      console.log(`   ❌ click() 실패: ${e}`);
+    }
+
+    await page.waitForTimeout(2000);
+
+    console.log('\n5️⃣ 최종 상태:');
+    console.log(`   URL: ${page.url()}`);
+    console.log(`   제목: ${await page.title()}`);
+  } else {
+    console.log('❌ 로그인 버튼을 찾을 수 없습니다!');
+  }
+
+  // 페이지 HTML 구조 확인
+  console.log('\n6️⃣ 전체 버튼 목록:');
+  const allButtons = page.locator('button');
+  const buttonCount = await allButtons.count();
+  console.log(`   총 버튼 개수: ${buttonCount}`);
+
+  for (let i = 0; i < Math.min(buttonCount, 5); i++) {
+    const btn = allButtons.nth(i);
+    const btnText = await btn.textContent();
+    console.log(`   [${i}] ${btnText?.trim()}`);
+  }
+});