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/lodash/_listCacheSet.js

@@ -0,0 +1,26 @@
+var assocIndexOf = require('./_assocIndexOf');
+
+/**
+ * Sets the list cache `key` to `value`.
+ *
+ * @private
+ * @name set
+ * @memberOf ListCache
+ * @param {string} key The key of the value to set.
+ * @param {*} value The value to set.
+ * @returns {Object} Returns the list cache instance.
+ */
+function listCacheSet(key, value) {
+  var data = this.__data__,
+      index = assocIndexOf(data, key);
+
+  if (index < 0) {
+    ++this.size;
+    data.push([key, value]);
+  } else {
+    data[index][1] = value;
+  }
+  return this;
+}
+
+module.exports = listCacheSet;