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/_stringSize.js

@@ -0,0 +1,18 @@
+var asciiSize = require('./_asciiSize'),
+    hasUnicode = require('./_hasUnicode'),
+    unicodeSize = require('./_unicodeSize');
+
+/**
+ * Gets the number of symbols in `string`.
+ *
+ * @private
+ * @param {string} string The string to inspect.
+ * @returns {number} Returns the string size.
+ */
+function stringSize(string) {
+  return hasUnicode(string)
+    ? unicodeSize(string)
+    : asciiSize(string);
+}
+
+module.exports = stringSize;