feat(web): add groups page with RouteManager and route handler proxies

Implements the Groups & Routes admin page with a client-side RouteManager
component (add/delete sync routes via fetch), server-side groups page that
pre-fetches groups/routes from the API, and Next.js Route Handler proxies
for /api/routes (GET, POST) and /api/routes/[id] (DELETE). Adds a custom
jest environment that polyfills Node 18+ native fetch into the jsdom sandbox
so tests can use jest.spyOn(global, 'fetch').

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web/jest.setup.ts

@@ -1 +1,7 @@
 import '@testing-library/jest-dom';
+import { configure } from '@testing-library/react';
+
+// Exclude <script>, <style>, and <option> elements from getByText queries.
+// <option> elements within <select> dropdowns would otherwise conflict with
+// route-name text in the route list when both contain the same group name.
+configure({ defaultIgnore: 'script, style, option' });