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/pad.js

@@ -0,0 +1,49 @@
+var createPadding = require('./_createPadding'),
+    stringSize = require('./_stringSize'),
+    toInteger = require('./toInteger'),
+    toString = require('./toString');
+
+/* Built-in method references for those with the same name as other `lodash` methods. */
+var nativeCeil = Math.ceil,
+    nativeFloor = Math.floor;
+
+/**
+ * Pads `string` on the left and right sides if it's shorter than `length`.
+ * Padding characters are truncated if they can't be evenly divided by `length`.
+ *
+ * @static
+ * @memberOf _
+ * @since 3.0.0
+ * @category String
+ * @param {string} [string=''] The string to pad.
+ * @param {number} [length=0] The padding length.
+ * @param {string} [chars=' '] The string used as padding.
+ * @returns {string} Returns the padded string.
+ * @example
+ *
+ * _.pad('abc', 8);
+ * // => '  abc   '
+ *
+ * _.pad('abc', 8, '_-');
+ * // => '_-abc_-_'
+ *
+ * _.pad('abc', 3);
+ * // => 'abc'
+ */
+function pad(string, length, chars) {
+  string = toString(string);
+  length = toInteger(length);
+
+  var strLength = length ? stringSize(string) : 0;
+  if (!length || strLength >= length) {
+    return string;
+  }
+  var mid = (length - strLength) / 2;
+  return (
+    createPadding(nativeFloor(mid), chars) +
+    string +
+    createPadding(nativeCeil(mid), chars)
+  );
+}
+
+module.exports = pad;