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/_createCaseFirst.js

@@ -0,0 +1,33 @@
+var castSlice = require('./_castSlice'),
+    hasUnicode = require('./_hasUnicode'),
+    stringToArray = require('./_stringToArray'),
+    toString = require('./toString');
+
+/**
+ * Creates a function like `_.lowerFirst`.
+ *
+ * @private
+ * @param {string} methodName The name of the `String` case method to use.
+ * @returns {Function} Returns the new case function.
+ */
+function createCaseFirst(methodName) {
+  return function(string) {
+    string = toString(string);
+
+    var strSymbols = hasUnicode(string)
+      ? stringToArray(string)
+      : undefined;
+
+    var chr = strSymbols
+      ? strSymbols[0]
+      : string.charAt(0);
+
+    var trailing = strSymbols
+      ? castSlice(strSymbols, 1).join('')
+      : string.slice(1);
+
+    return chr[methodName]() + trailing;
+  };
+}
+
+module.exports = createCaseFirst;