feat: add diff review dialog, undo support, and monitoring panels}
- Add diff dialog with inline and side-by-side views for reviewing
changes before saving (Angular + React), gated by new setting
- Add undo support for string and JSON key saves via toast action
with 5-second window to revert to previous value
- Add server info, persistence, replication, keyspace, CPU, and
loaded modules panels to the monitoring/pulse page
- Add "undo enabled" and "show diff before save" toggle settings
to tree settings dialog and settings page
- Add `diff` (v8.0.4) and `@types/diff` dependencies
- Add diff, undo, and monitoring i18n strings across all 54 languages
- Bump version to v2026.4.422