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/v8-to-istanbul/lib/line.js

@@ -0,0 +1,34 @@
+module.exports = class CovLine {
+  constructor (line, startCol, lineStr) {
+    this.line = line
+    // note that startCol and endCol are absolute positions
+    // within a file, not relative to the line.
+    this.startCol = startCol
+
+    // the line length itself does not include the newline characters,
+    // these are however taken into account when enumerating absolute offset.
+    const matchedNewLineChar = lineStr.match(/\r?\n$/u)
+    const newLineLength = matchedNewLineChar ? matchedNewLineChar[0].length : 0
+    this.endCol = startCol + lineStr.length - newLineLength
+
+    // we start with all lines having been executed, and work
+    // backwards zeroing out lines based on V8 output.
+    this.count = 1
+
+    // set by source.js during parsing, if /* c8 ignore next */ is found.
+    this.ignore = false
+  }
+
+  toIstanbul () {
+    return {
+      start: {
+        line: this.line,
+        column: 0
+      },
+      end: {
+        line: this.line,
+        column: this.endCol - this.startCol
+      }
+    }
+  }
+}