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/convertor/create.cjs

@@ -0,0 +1,32 @@
+'use strict';
+
+const List = require('../utils/List.cjs');
+
+function createConvertor(walk) {
+    return {
+        fromPlainObject(ast) {
+            walk(ast, {
+                enter(node) {
+                    if (node.children && node.children instanceof List.List === false) {
+                        node.children = new List.List().fromArray(node.children);
+                    }
+                }
+            });
+
+            return ast;
+        },
+        toPlainObject(ast) {
+            walk(ast, {
+                leave(node) {
+                    if (node.children && node.children instanceof List.List) {
+                        node.children = node.children.toArray();
+                    }
+                }
+            });
+
+            return ast;
+        }
+    };
+}
+
+exports.createConvertor = createConvertor;

frontend/node_modules/css-tree/cjs/convertor/index.cjs

@@ -0,0 +1,8 @@
+'use strict';
+
+const create = require('./create.cjs');
+const index$1 = require('../walker/index.cjs');
+
+const index = create.createConvertor(index$1);
+
+module.exports = index;