feat(localization): add Russian (ru) translations

Add Russian localization for the Stream Chat widgets, implementing
StreamChatLocalizationsRu against the v10 localization interface with
proper Russian plural forms (one/few/many) for count-based strings, and
registering the `ru` locale. Update the README and changelog accordingly.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: Emil Valiyev

packages/stream_chat_localizations/CHANGELOG.md

@@ -3,6 +3,7 @@
 ✅ Added
 
 - Added Azerbaijani (`az`) translations.
+- Added Russian (`ru`) translations.
 
 ## 10.0.1
 

packages/stream_chat_localizations/README.md

@@ -34,6 +34,7 @@ This package provides localized strings for all Stream Chat Flutter widgets. Dep
 - [German](https://github.com/GetStream/stream-chat-flutter/blob/master/packages/stream_chat_localizations/lib/src/stream_chat_localizations_de.dart)
 - [Norwegian](https://github.com/GetStream/stream-chat-flutter/blob/master/packages/stream_chat_localizations/lib/src/stream_chat_localizations_no.dart)
 - [Azerbaijani](https://github.com/GetStream/stream-chat-flutter/blob/master/packages/stream_chat_localizations/lib/src/stream_chat_localizations_az.dart)
+- [Russian](https://github.com/GetStream/stream-chat-flutter/blob/master/packages/stream_chat_localizations/lib/src/stream_chat_localizations_ru.dart)
 
 More languages will be added in the future. Feel free to [contribute](https://github.com/GetStream/stream-chat-flutter/blob/master/CONTRIBUTING.md) to add more.
 
@@ -81,6 +82,7 @@ class MyApp extends StatelessWidget {
         Locale('de'),
         Locale('no'),
         Locale('az'),
+        Locale('ru'),
       ],
       // Add GlobalStreamChatLocalizations.delegates
       localizationsDelegates: GlobalStreamChatLocalizations.delegates,
@@ -130,6 +132,7 @@ Example:
   <string>de</string>
   <string>no</string>
   <string>az</string>
+  <string>ru</string>
 </array>
 ```
 

packages/stream_chat_localizations/lib/src/stream_chat_localizations.dart

@@ -15,6 +15,7 @@ part 'stream_chat_localizations_ja.dart';
 part 'stream_chat_localizations_ko.dart';
 part 'stream_chat_localizations_pt.dart';
 part 'stream_chat_localizations_no.dart';
+part 'stream_chat_localizations_ru.dart';
 
 /// The set of supported languages, as language code strings.
 ///
@@ -37,6 +38,7 @@ const kStreamChatSupportedLanguages = {
   'pt',
   'de',
   'no',
+  'ru',
 };
 
 /// Creates a [GlobalStreamChatLocalizations] instance for the given `locale`.
@@ -83,6 +85,8 @@ GlobalStreamChatLocalizations? getStreamChatTranslation(Locale locale) {
       return const StreamChatLocalizationsDe();
     case 'no':
       return const StreamChatLocalizationsNo();
+    case 'ru':
+      return const StreamChatLocalizationsRu();
     default:
       return null;
   }