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/dom-helpers/cjs/transitionEnd.js

@@ -0,0 +1,50 @@
+"use strict";
+
+var _interopRequireDefault = require("@babel/runtime/helpers/interopRequireDefault");
+
+exports.__esModule = true;
+exports.default = transitionEnd;
+
+var _css = _interopRequireDefault(require("./css"));
+
+var _listen = _interopRequireDefault(require("./listen"));
+
+var _triggerEvent = _interopRequireDefault(require("./triggerEvent"));
+
+function parseDuration(node) {
+  var str = (0, _css.default)(node, 'transitionDuration') || '';
+  var mult = str.indexOf('ms') === -1 ? 1000 : 1;
+  return parseFloat(str) * mult;
+}
+
+function emulateTransitionEnd(element, duration, padding) {
+  if (padding === void 0) {
+    padding = 5;
+  }
+
+  var called = false;
+  var handle = setTimeout(function () {
+    if (!called) (0, _triggerEvent.default)(element, 'transitionend', true);
+  }, duration + padding);
+  var remove = (0, _listen.default)(element, 'transitionend', function () {
+    called = true;
+  }, {
+    once: true
+  });
+  return function () {
+    clearTimeout(handle);
+    remove();
+  };
+}
+
+function transitionEnd(element, handler, duration, padding) {
+  if (duration == null) duration = parseDuration(element) || 0;
+  var removeEmulate = emulateTransitionEnd(element, duration, padding);
+  var remove = (0, _listen.default)(element, 'transitionend', handler);
+  return function () {
+    removeEmulate();
+    remove();
+  };
+}
+
+module.exports = exports["default"];