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.config.js

@@ -4,6 +4,8 @@ const createJestConfig = nextJest({ dir: './' });
 
 module.exports = createJestConfig({
   setupFilesAfterEnv: ['<rootDir>/jest.setup.ts'],
-  testEnvironment: 'jest-environment-jsdom',
+  // Custom environment that extends jest-environment-jsdom and polyfills the
+  // native Node 18+ Fetch API so tests can use jest.spyOn(global, 'fetch').
+  testEnvironment: '<rootDir>/jest.environment.js',
   testMatch: ['**/*.test.tsx', '**/*.test.ts'],
 });