Add visual indicators so users can distinguish readonly connections from read-write connections at a glance: - Sidebar: show a lock icon badge on readonly connection nodes - Tab bar: show a lock icon with tooltip on tabs with readonly connections - Add isConnectionReadonly() helper in tabPresentation.ts - Add readOnlyBadge i18n key for all 6 locales (en, zh-CN, zh-TW, es, it, pt-BR)