feat(frontend): add API client, layout, and routing

- Create Axios-based API client with sources, jobs, and dashboard endpoints
- Add responsive Layout component with navigation sidebar
- Set up React Router with Dashboard, Backups, and Settings routes
- Configure TanStack Query provider with default options
- Use lucide-react for navigation icons

frontend/node_modules/cssstyle/lib/utils/propertyDescriptors.js

@@ -0,0 +1,16 @@
+"use strict";
+
+const prepareValue = require("../parsers").prepareValue;
+
+module.exports.getPropertyDescriptor = function getPropertyDescriptor(property) {
+  return {
+    set(v) {
+      this._setProperty(property, prepareValue(v));
+    },
+    get() {
+      return this.getPropertyValue(property);
+    },
+    enumerable: true,
+    configurable: true
+  };
+};