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/css-tree/cjs/syntax/function/expression.cjs

@@ -0,0 +1,11 @@
+'use strict';
+
+// legacy IE function
+// expression( <any-value> )
+function expressionFn() {
+    return this.createSingleNodeList(
+        this.Raw(this.tokenIndex, null, false)
+    );
+}
+
+module.exports = expressionFn;