✨ task-buffmanager: add world event mode

[koji-assistant]

Summary

• add /buffevent admin command for server-wide buff events
• support start/stop/status, random package selection, configurable default duration, and optional announcements
• apply active world events to late joiners
• maintain active world events in the BuffManager cron and remove them when expired
• reuse EOS_ game IDs for 7D2D buff/debuff commands

Testing

• npm ci --legacy-peer-deps
• npm run build
• npm run typecheck
• node dist/scripts/module-to-json.js modules/BuffManager /tmp/buffmanager-export.json
• node --check on all BuffManager command/hook/cron/function JS files

Note: full npm test was attempted, but this local environment cannot reach the test stack: WebSocket 503 and Redis ECONNREFUSED 127.0.0.1:6383.