feat(i18n): add initial Russian localization for documentation and site config

- Added full Russian translations for all main documentation sections () into .
- Sections translated include: key features, installation, getting started, all core concepts, advanced features, API reference, FAQ, links, additional modules, contributing, and license.
- Updated  to ensure language switching is available and Russian locale is active.
- Each Russian file preserves the structure and formatting of the original Markdown, with machine-aided draft translation for immediate use.
- Lays the groundwork for UI language switching (en/ru) and enables further manual translation refinement and review.

website/i18n/ru/docusaurus-plugin-content-docs/current/installation.md

@@ -0,0 +1,18 @@
+---
+sidebar_position: 2
+---
+
+# Установка
+
+Добавьте в ваш `pubspec.yaml`:
+
+```yaml
+dependencies:
+  cherrypick: ^<latest_version>
+```
+
+Затем выполните команду:
+
+```shell
+dart pub get
+```