Set up comprehensive frontend testing infrastructure

- Install Jest for unit testing with React Testing Library
- Install Playwright for end-to-end testing
- Configure Jest with proper TypeScript support and module mapping
- Create test setup files and utilities for both unit and e2e tests

Components:
* Jest configuration with coverage thresholds
* Playwright configuration with browser automation
* Unit tests for LoginForm, AuthContext, and useSocketIO hook
* E2E tests for authentication, dashboard, and agents workflows
* GitHub Actions workflow for automated testing
* Mock data and API utilities for consistent testing
* Test documentation with best practices

Testing features:
- Unit tests with 70% coverage threshold
- E2E tests with API mocking and user journey testing
- CI/CD integration for automated test runs
- Cross-browser testing support with Playwright
- Authentication system testing end-to-end

🚀 Generated with [Claude Code](https://claude.ai/code)

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

frontend/node_modules/@testing-library/user-event/dist/esm/document/prepareDocument.js

@@ -0,0 +1,56 @@
+import { dispatchDOMEvent } from '../event/dispatchEvent.js';
+import { isElementType } from '../utils/misc/isElementType.js';
+import '../utils/dataTransfer/Clipboard.js';
+import { getInitialValue, clearInitialValue } from './UI.js';
+import '@testing-library/dom';
+import { prepareValueInterceptor, prepareSelectionInterceptor, prepareRangeTextInterceptor } from './interceptor.js';
+
+const isPrepared = Symbol('Node prepared with document state workarounds');
+function prepareDocument(document) {
+    if (document[isPrepared]) {
+        return;
+    }
+    document.addEventListener('focus', (e)=>{
+        const el = e.target;
+        prepareElement(el);
+    }, {
+        capture: true,
+        passive: true
+    });
+    // Our test environment defaults to `document.body` as `activeElement`.
+    // In other environments this might be `null` when preparing.
+    // istanbul ignore else
+    if (document.activeElement) {
+        prepareElement(document.activeElement);
+    }
+    document.addEventListener('blur', (e)=>{
+        const el = e.target;
+        const initialValue = getInitialValue(el);
+        if (initialValue !== undefined) {
+            if (el.value !== initialValue) {
+                dispatchDOMEvent(el, 'change');
+            }
+            clearInitialValue(el);
+        }
+    }, {
+        capture: true,
+        passive: true
+    });
+    document[isPrepared] = isPrepared;
+}
+function prepareElement(el) {
+    if (el[isPrepared]) {
+        return;
+    }
+    if (isElementType(el, [
+        'input',
+        'textarea'
+    ])) {
+        prepareValueInterceptor(el);
+        prepareSelectionInterceptor(el);
+        prepareRangeTextInterceptor(el);
+    }
+    el[isPrepared] = isPrepared;
+}
+
+export { prepareDocument };