Role sync and group ranks

Map platform roles to Discord roles on the Discord page, and to Roblox group ranks on Roblox Groups. Changing someone's role then queues updates, retried with backoff and visible per member on the staff list.

• Roles with Administrator or Manage Server are synced only after the owner turns on Allow syncing admin roles for that server. The sync re-checks every time and removes such a role rather than hand it out without that opt-in.
• Force role sync takes back roles or ranks given by hand to people the platform does not give them to, and tells whoever did it to use /whitelist or the dashboard.
• Per-member exceptions leave one person out of Discord role sync or group rank sync.
• Discord roles and group ranks never grant platform permissions.