feat(webhooks): add signature-verified GitHub webhook route

packages/backend/convex/http.ts

@@ -1,9 +1,16 @@
 import { httpRouter } from 'convex/server';
 
 import { auth } from './auth';
+import { handleGithubWebhook } from './githubWebhooks';
 
 const http = httpRouter();
 
 auth.addHttpRoutes(http);
 
+http.route({
+  path: '/webhooks/github',
+  method: 'POST',
+  handler: handleGithubWebhook,
+});
+
 export default http;