- S1: Add composite index (is_active, is_dismissed, remind_at) for /due query performance with multi-user scaling - W3: Snooze endpoint rejects dismissed/inactive reminders (409) - W4: Custom field_validator on ReminderSnooze for clear error message - S2: aria-label on all snooze/dismiss buttons in banner and toasts Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>