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/whatwg-url/lib/infra.js

@@ -0,0 +1,26 @@
+"use strict";
+
+// Note that we take code points as JS numbers, not JS strings.
+
+function isASCIIDigit(c) {
+  return c >= 0x30 && c <= 0x39;
+}
+
+function isASCIIAlpha(c) {
+  return (c >= 0x41 && c <= 0x5A) || (c >= 0x61 && c <= 0x7A);
+}
+
+function isASCIIAlphanumeric(c) {
+  return isASCIIAlpha(c) || isASCIIDigit(c);
+}
+
+function isASCIIHex(c) {
+  return isASCIIDigit(c) || (c >= 0x41 && c <= 0x46) || (c >= 0x61 && c <= 0x66);
+}
+
+module.exports = {
+  isASCIIDigit,
+  isASCIIAlpha,
+  isASCIIAlphanumeric,
+  isASCIIHex
+};