test: add initial Cypress e2e test infrastructure

Smoke tests for verifying Cypress runs, plus basic API tests
for health and sessions endpoints.

cypress/support/e2e.js

@@ -0,0 +1,5 @@
+// Cypress E2E support file
+// Add custom commands and global hooks here
+
+// Prevent Cypress from failing on uncaught exceptions from the app
+Cypress.on('uncaught:exception', () => false);