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/node/Selector.cjs

@@ -0,0 +1,39 @@
+'use strict';
+
+const name = 'Selector';
+const structure = {
+    children: [[
+        'TypeSelector',
+        'IdSelector',
+        'ClassSelector',
+        'AttributeSelector',
+        'PseudoClassSelector',
+        'PseudoElementSelector',
+        'Combinator',
+        'WhiteSpace'
+    ]]
+};
+
+function parse() {
+    const children = this.readSequence(this.scope.Selector);
+
+    // nothing were consumed
+    if (this.getFirstListNode(children) === null) {
+        this.error('Selector is expected');
+    }
+
+    return {
+        type: 'Selector',
+        loc: this.getLocationFromList(children),
+        children
+    };
+}
+
+function generate(node) {
+    this.children(node);
+}
+
+exports.generate = generate;
+exports.name = name;
+exports.parse = parse;
+exports.structure = structure;