Группы: приглашения вместо авто-добавления (согласиться/отказаться)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/api/queryKeys.ts

@@ -15,6 +15,7 @@ export const qk = {
   groupStats: (id: number) => ["group", id, "stats"] as const,
   match: (id: number) => ["match", id] as const,
   authConfig: ["authConfig"] as const,
+  invitations: ["invitations"] as const,
   devUsers: ["devUsers"] as const,
   adminUsers: ["adminUsers"] as const,
   adminGroups: ["adminGroups"] as const,