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/dom-helpers/esm/css.js

@@ -0,0 +1,32 @@
+import getComputedStyle from './getComputedStyle';
+import hyphenate from './hyphenateStyle';
+import isTransform from './isTransform';
+
+function style(node, property) {
+  var css = '';
+  var transforms = '';
+
+  if (typeof property === 'string') {
+    return node.style.getPropertyValue(hyphenate(property)) || getComputedStyle(node).getPropertyValue(hyphenate(property));
+  }
+
+  Object.keys(property).forEach(function (key) {
+    var value = property[key];
+
+    if (!value && value !== 0) {
+      node.style.removeProperty(hyphenate(key));
+    } else if (isTransform(key)) {
+      transforms += key + "(" + value + ") ";
+    } else {
+      css += hyphenate(key) + ": " + value + ";";
+    }
+  });
+
+  if (transforms) {
+    css += "transform: " + transforms + ";";
+  }
+
+  node.style.cssText += ";" + css;
+}
+
+export default style;