fix(e2e): resolve admin user journey authentication and stabilize flaky tests

- Fix loginAdminAndSetCookie to set both cookie (middleware) and localStorage (auth-context)
- Add page navigation before localStorage evaluate to avoid SecurityError
- Update Playwright webServer to npm run dev for API route support
- Fix UJ-10 CSS selector parsing error (text= regex mixed with CSS)
- Fix cases-filter flaky test (getByRole('radio') → locator('button[role="radio"]'))
- Update test-strategy-plan.md: mark UJ-03/06/07 as ✅ completed
- Update README.md with admin fix progress record

e2e/playwright.config.ts

@@ -102,7 +102,9 @@ export default defineConfig({
     },
   ],
   webServer: {
-    command: 'npm run preview',
+    // 使用 dev server 以支持 API 路由（admin 用户旅程等测试需要）
+    // 若只运行非 API 测试（如 @journey @regression），可手动启动 npm run preview 并设置 reuseExistingServer: true
+    command: 'npm run dev',
     url: 'http://localhost:3000',
     reuseExistingServer: true,
     timeout: 120000,