docs: update v2026.4.306 changelog with detailed release notes}
- Replace placeholder changelog entries with comprehensive release notes - Document ReJSON (JSON data type) support features: view, create, edit, format, copy, and download JSON documents - Document auto-detection of Redis modules via MODULE LIST - Document JSON keys tree icon and Add Key dialog support - Document Electron webview to iframe migration refactor - Document OnPush change detection and markForCheck refactors - Document bugfixes for Electron loading spinner, search filter restore, and Add Key dialog prefix - Document i18n additions for 21 languages and README updates - Document removal of armv7l (32-bit ARM) build targets