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/@tanstack/react-query/build/query-codemods/eslint.config.js

@@ -0,0 +1,18 @@
+// @ts-check
+
+import rootConfig from './root.eslint.config.js'
+
+export default [
+  ...rootConfig,
+  {
+    rules: {
+      'cspell/spellchecker': 'off',
+      '@typescript-eslint/no-unnecessary-condition': 'off',
+      'import/no-duplicates': 'off',
+      'import/no-unresolved': 'off',
+      'import/order': 'off',
+      'no-shadow': 'off',
+      'sort-imports': 'off',
+    },
+  },
+]