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/is-stream/index.js

@@ -0,0 +1,29 @@
+export function isStream(stream) {
+	return stream !== null
+		&& typeof stream === 'object'
+		&& typeof stream.pipe === 'function';
+}
+
+export function isWritableStream(stream) {
+	return isStream(stream)
+		&& stream.writable !== false
+		&& typeof stream._write === 'function'
+		&& typeof stream._writableState === 'object';
+}
+
+export function isReadableStream(stream) {
+	return isStream(stream)
+		&& stream.readable !== false
+		&& typeof stream._read === 'function'
+		&& typeof stream._readableState === 'object';
+}
+
+export function isDuplexStream(stream) {
+	return isWritableStream(stream)
+		&& isReadableStream(stream);
+}
+
+export function isTransformStream(stream) {
+	return isDuplexStream(stream)
+		&& typeof stream._transform === 'function';
+}