Award shortlist UX improvements + configurable invite link expiry

Award shortlist:
- Expandable reasoning text (click to toggle, hover hint)
- Bulk select/deselect all checkbox in header
- Top N projects highlighted with amber background
- New bulkToggleShortlisted backend mutation

Invite link expiry:
- New "Invitation Link Expiry (hours)" field in Security Settings
- Reads from systemSettings `invite_link_expiry_hours` (default 72h / 3 days)
- Email template dynamically shows "X hours" or "X days" based on setting
- All 3 invite paths (bulk create, single invite, bulk resend) use setting

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/settings/settings-content.tsx

@@ -115,6 +115,7 @@ export function SettingsContent({ initialSettings, isSuperAdmin = true }: Settin
   const securitySettings = getSettingsByKeys([
     'session_duration_hours',
     'magic_link_expiry_minutes',
+    'invite_link_expiry_hours',
     'rate_limit_requests_per_minute',
   ])