docs: rewrite changelog for v2026.4.342 with detailed entries}
- Replace placeholder documentation-only entries with comprehensive feature, refactor, bugfix, and performance changelog items - Add RediSearch full-text search UI, monitoring dashboard, key export/import, connection groups, keyboard shortcuts, theme auto-switch, and hamburger menu features - Document route rename (/main to /database), cookie-to-localStorage migration, and jquery/ to overlay/ directory rename refactors - Add bugfixes for auto-theme persistence, Grunt submodule versioning, and modules tab in statistics - Add performance entry for batched key import using Redis pipelines - Remove intermediate v2026.4.340 section, consolidating into v2026.4.342