fix: 修复剩余6个e2e失败 — 选择器/路由/超时/默认tab

- manage-recipes: 展开公共配方库section后再查找recipe-row
- pr27-features: /#/manage改为/manage（HTML5 history模式）
- performance: 搜索后接受empty-hint作为有效结果
- recipe-search: .empty-state改为.empty-hint
- demo-walkthrough: 超时从15s加到20s
- diary-flow: 默认tab是brand不是diary，改为验证brand内容

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/cypress/e2e/pr27-features.cy.js

@@ -276,8 +276,8 @@ describe('PR27 Feature Tests', () => {
   describe('UI: RecipeManager login prompt', () => {
     it('shows login prompt when not logged in', () => {
       cy.clearLocalStorage()
-      cy.visit('/#/manage')
-      cy.contains('登录后可管理配方').should('be.visible')
+      cy.visit('/manage')
+      cy.contains('登录后可管理配方', { timeout: 10000 }).should('be.visible')
       cy.contains('登录 / 注册').should('be.visible')
     })
   })