fix: 修复全部27个失败的e2e测试

根本原因: 所有测试硬编码了只在生产环境有效的admin token，
CI创建新数据库时token不同导致全部认证失败。

修复:
- CI: 设置已知ADMIN_TOKEN环境变量传给后端和Cypress
- cypress/support/e2e.js: 新增cy.getAdminToken()动态获取token
- 24个spec文件: 硬编码token改为cy.getAdminToken()
- UI选择器: 适配管理页面从tab移到UserMenu、编辑器DOM变化
- API: create_recipe→share_recipe、ingredients格式、权限变化
- 超时: 300s→420s适应32个spec

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

frontend/cypress/e2e/registration-flow.cy.js

@@ -1,15 +1,21 @@
 describe('Registration Flow', () => {
-  const ADMIN_TOKEN = 'c86ae7afbe10fabe3c1d5e1a7fee74feaadfd5dc7be2ab62'
-  const authHeaders = { Authorization: `Bearer ${ADMIN_TOKEN}` }
+  let adminToken
+  let authHeaders
   const TEST_USER = 'cypress_test_register_' + Date.now()
 
+  before(() => {
+    cy.getAdminToken().then(token => {
+      adminToken = token
+      authHeaders = { Authorization: `Bearer ${token}` }
+    })
+  })
+
   it('can register a new user via API', () => {
     cy.request({
       method: 'POST', url: '/api/register',
-      body: { username: TEST_USER, password: 'test1234', display_name: 'Cypress注册测试' },
+      body: { username: TEST_USER, password: 'test1234' },
       failOnStatusCode: false
     }).then(res => {
-      // Registration may or may not be implemented
       if (res.status === 200 || res.status === 201) {
         expect(res.body).to.have.property('token')
       }
@@ -32,11 +38,10 @@ describe('Registration Flow', () => {
   it('rejects duplicate username', () => {
     cy.request({
       method: 'POST', url: '/api/register',
-      body: { username: TEST_USER, password: 'another123', display_name: 'Duplicate' },
+      body: { username: TEST_USER, password: 'another123' },
       failOnStatusCode: false
     }).then(res => {
-      // Should fail with 400 or 409
-      if (res.status !== 404) { // 404 means register endpoint doesn't exist
+      if (res.status !== 404) {
         expect(res.status).to.be.oneOf([400, 409, 422])
       }
     })