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/data-urls/lib/utils.js

@@ -0,0 +1,20 @@
+"use strict";
+
+exports.stripLeadingAndTrailingASCIIWhitespace = string => {
+  return string.replace(/^[ \t\n\f\r]+/u, "").replace(/[ \t\n\f\r]+$/u, "");
+};
+
+exports.isomorphicDecode = input => {
+  return Array.from(input, byte => String.fromCodePoint(byte)).join("");
+};
+
+exports.forgivingBase64Decode = data => {
+  let asString;
+  try {
+    asString = atob(data);
+  } catch {
+    return null;
+  }
+
+  return Uint8Array.from(asString, c => c.codePointAt(0));
+};