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/tailwindcss/lib/postcss-plugins/nesting/index.js

@@ -0,0 +1,21 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", {
+    value: true
+});
+Object.defineProperty(exports, "default", {
+    enumerable: true,
+    get: function() {
+        return _default;
+    }
+});
+const _plugin = require("./plugin");
+const _default = Object.assign(function(opts) {
+    return {
+        postcssPlugin: "tailwindcss/nesting",
+        Once (root, { result  }) {
+            return (0, _plugin.nesting)(opts)(root, result);
+        }
+    };
+}, {
+    postcss: true
+});