feat: jwt cache, redis health, help-ticket admin, and write rate limits

Cut Auth.js DB load with cached jwtVersion checks, surface Redis in /api/health and deploy warnings, add admin help-center ticket reply UI, rate-limit API tickets/reactions/referral claims, and revoke PATs on sign-out-everywhere.

Co-authored-by: Cursor <[email protected]>

src/types/next-auth.d.ts

@@ -10,6 +10,7 @@ declare module "next-auth/jwt" {
 	interface JWT {
 		rank?: number;
 		jwtVersion?: number;
+		jwtCheckedAt?: number;
 		invalid?: boolean;
 	}
 }