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/vitest/globals.d.ts

@@ -0,0 +1,19 @@
+declare global {
+  const suite: typeof import('vitest')['suite']
+  const test: typeof import('vitest')['test']
+  const describe: typeof import('vitest')['describe']
+  const it: typeof import('vitest')['it']
+  const expectTypeOf: typeof import('vitest')['expectTypeOf']
+  const assertType: typeof import('vitest')['assertType']
+  const expect: typeof import('vitest')['expect']
+  const assert: typeof import('vitest')['assert']
+  const vitest: typeof import('vitest')['vitest']
+  const vi: typeof import('vitest')['vitest']
+  const beforeAll: typeof import('vitest')['beforeAll']
+  const afterAll: typeof import('vitest')['afterAll']
+  const beforeEach: typeof import('vitest')['beforeEach']
+  const afterEach: typeof import('vitest')['afterEach']
+  const onTestFailed: typeof import('vitest')['onTestFailed']
+  const onTestFinished: typeof import('vitest')['onTestFinished']
+}
+export {}