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/entities/src/escape.spec.ts

@@ -0,0 +1,14 @@
+import { describe, it, expect } from "vitest";
+import * as entities from "./index.js";
+
+describe("escape HTML", () => {
+    it("should escape HTML attribute values", () =>
+        expect(entities.escapeAttribute('<a " attr > & value \u00A0!')).toBe(
+            "<a &quot; attr > &amp; value &nbsp;!",
+        ));
+
+    it("should escape HTML text", () =>
+        expect(entities.escapeText('<a " text > & value \u00A0!')).toBe(
+            '&lt;a " text &gt; &amp; value &nbsp;!',
+        ));
+});