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/cssstyle/lib/properties/backgroundPosition.js

@@ -0,0 +1,52 @@
+"use strict";
+
+const parsers = require("../parsers");
+
+module.exports.parse = function parse(v) {
+  const parts = parsers.splitValue(v);
+  if (!parts.length || parts.length > 2) {
+    return;
+  }
+  const validKeywordsX = ["left", "center", "right"];
+  const validKeywordsY = ["top", "center", "bottom"];
+  if (parts.length === 1) {
+    const dim = parsers.parseMeasurement(parts[0]);
+    if (dim) {
+      return dim;
+    }
+    const validKeywords = new Set([...validKeywordsX, ...validKeywordsY]);
+    return parsers.parseKeyword(v, [...validKeywords]);
+  }
+  const [partX, partY] = parts;
+  const posX = parsers.parseMeasurement(partX) || parsers.parseKeyword(partX, validKeywordsX);
+  if (posX) {
+    const posY = parsers.parseMeasurement(partY) || parsers.parseKeyword(partY, validKeywordsY);
+    if (posY) {
+      return `${posX} ${posY}`;
+    }
+  }
+};
+
+module.exports.isValid = function isValid(v) {
+  if (v === "") {
+    return true;
+  }
+  return typeof module.exports.parse(v) === "string";
+};
+
+module.exports.definition = {
+  set(v) {
+    v = parsers.prepareValue(v, this._global);
+    if (parsers.hasVarFunc(v)) {
+      this._setProperty("background", "");
+      this._setProperty("background-position", v);
+    } else {
+      this._setProperty("background-position", module.exports.parse(v));
+    }
+  },
+  get() {
+    return this.getPropertyValue("background-position");
+  },
+  enumerable: true,
+  configurable: true
+};