automation/meeting-reminders: meetings made by talking to the agent, reminded in Telegram #5418

Owner's ask: online and offline meetings made through the agent, with proactive Telegram reminders for the person. Spec: specs/automation/meeting-reminders.t27 (PR #5390). Host: 999-multibots-telegraf render src/agent/meetings.ts (merged, live). Claim: RUN_LIVE = false until a real reminder reaches a real chat.