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/shebang-regex/index.d.ts

@@ -0,0 +1,22 @@
+/**
+Regular expression for matching a [shebang](https://en.wikipedia.org/wiki/Shebang_(Unix)) line.
+
+@example
+```
+import shebangRegex = require('shebang-regex');
+
+const string = '#!/usr/bin/env node\nconsole.log("unicorns");';
+
+shebangRegex.test(string);
+//=> true
+
+shebangRegex.exec(string)[0];
+//=> '#!/usr/bin/env node'
+
+shebangRegex.exec(string)[1];
+//=> '/usr/bin/env node'
+```
+*/
+declare const shebangRegex: RegExp;
+
+export = shebangRegex;