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/util/responsive.js

@@ -0,0 +1,24 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", {
+    value: true
+});
+Object.defineProperty(exports, "default", {
+    enumerable: true,
+    get: function() {
+        return responsive;
+    }
+});
+const _postcss = /*#__PURE__*/ _interop_require_default(require("postcss"));
+const _cloneNodes = /*#__PURE__*/ _interop_require_default(require("./cloneNodes"));
+function _interop_require_default(obj) {
+    return obj && obj.__esModule ? obj : {
+        default: obj
+    };
+}
+function responsive(rules) {
+    return _postcss.default.atRule({
+        name: "responsive"
+    }).append((0, _cloneNodes.default)(Array.isArray(rules) ? rules : [
+        rules
+    ]));
+}