Add E2E tests for logout, account CRUD, and file operations

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cypress/fixtures/api/user-detail.json

@@ -0,0 +1,11 @@
+{
+  "username": "testadmin",
+  "name": "Test Admin",
+  "is_admin": true,
+  "is_active": true,
+  "is_sso": false,
+  "has_data": true,
+  "roles": [
+    { "code": "admin", "name": "Administrator" }
+  ]
+}