test: add initial Cypress e2e test infrastructure

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

cypress.config.js

@@ -0,0 +1,12 @@
+const { defineConfig } = require('cypress');
+
+module.exports = defineConfig({
+    e2e: {
+        supportFile: 'cypress/support/e2e.js',
+        specPattern: 'cypress/e2e/**/*.cy.{js,ts}',
+        defaultCommandTimeout: 10000,
+        requestTimeout: 10000,
+        video: false,
+        screenshotOnRunFailure: true,
+    },
+});