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/d3-array/src/greatestIndex.js

@@ -0,0 +1,19 @@
+import ascending from "./ascending.js";
+import maxIndex from "./maxIndex.js";
+
+export default function greatestIndex(values, compare = ascending) {
+  if (compare.length === 1) return maxIndex(values, compare);
+  let maxValue;
+  let max = -1;
+  let index = -1;
+  for (const value of values) {
+    ++index;
+    if (max < 0
+        ? compare(value, value) === 0
+        : compare(value, maxValue) > 0) {
+      maxValue = value;
+      max = index;
+    }
+  }
+  return max;
+}