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/@testing-library/dom/dist/config.js

@@ -0,0 +1,67 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.configure = configure;
+exports.getConfig = getConfig;
+exports.runWithExpensiveErrorDiagnosticsDisabled = runWithExpensiveErrorDiagnosticsDisabled;
+var _prettyDom = require("./pretty-dom");
+// It would be cleaner for this to live inside './queries', but
+// other parts of the code assume that all exports from
+// './queries' are query functions.
+let config = {
+  testIdAttribute: 'data-testid',
+  asyncUtilTimeout: 1000,
+  // asyncWrapper and advanceTimersWrapper is to support React's async `act` function.
+  // forcing react-testing-library to wrap all async functions would've been
+  // a total nightmare (consider wrapping every findBy* query and then also
+  // updating `within` so those would be wrapped too. Total nightmare).
+  // so we have this config option that's really only intended for
+  // react-testing-library to use. For that reason, this feature will remain
+  // undocumented.
+  asyncWrapper: cb => cb(),
+  unstable_advanceTimersWrapper: cb => cb(),
+  eventWrapper: cb => cb(),
+  // default value for the `hidden` option in `ByRole` queries
+  defaultHidden: false,
+  // default value for the `ignore` option in `ByText` queries
+  defaultIgnore: 'script, style',
+  // showOriginalStackTrace flag to show the full error stack traces for async errors
+  showOriginalStackTrace: false,
+  // throw errors w/ suggestions for better queries. Opt in so off by default.
+  throwSuggestions: false,
+  // called when getBy* queries fail. (message, container) => Error
+  getElementError(message, container) {
+    const prettifiedDOM = (0, _prettyDom.prettyDOM)(container);
+    const error = new Error([message, `Ignored nodes: comments, ${config.defaultIgnore}\n${prettifiedDOM}`].filter(Boolean).join('\n\n'));
+    error.name = 'TestingLibraryElementError';
+    return error;
+  },
+  _disableExpensiveErrorDiagnostics: false,
+  computedStyleSupportsPseudoElements: false
+};
+function runWithExpensiveErrorDiagnosticsDisabled(callback) {
+  try {
+    config._disableExpensiveErrorDiagnostics = true;
+    return callback();
+  } finally {
+    config._disableExpensiveErrorDiagnostics = false;
+  }
+}
+function configure(newConfig) {
+  if (typeof newConfig === 'function') {
+    // Pass the existing config out to the provided function
+    // and accept a delta in return
+    newConfig = newConfig(config);
+  }
+
+  // Merge the incoming config delta
+  config = {
+    ...config,
+    ...newConfig
+  };
+}
+function getConfig() {
+  return config;
+}