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/_trimmedEndIndex.js

@@ -0,0 +1,19 @@
+/** Used to match a single whitespace character. */
+var reWhitespace = /\s/;
+
+/**
+ * Used by `_.trim` and `_.trimEnd` to get the index of the last non-whitespace
+ * character of `string`.
+ *
+ * @private
+ * @param {string} string The string to inspect.
+ * @returns {number} Returns the index of the last non-whitespace character.
+ */
+function trimmedEndIndex(string) {
+  var index = string.length;
+
+  while (index-- && reWhitespace.test(string.charAt(index))) {}
+  return index;
+}
+
+module.exports = trimmedEndIndex;