Sends one-shot DMs once a mission is evaluable asking members to rate their leadership (and leaders to rate subordinates), gated by a new evaluationRemindersSentAt marker on Missions with its migration. Adds the /remind-evaluations staff command (manual trigger/sweep) and DISCORD_EVALUATION_POLL_MS config; updates bot and root docs.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
