feat(i18n): localize start/help/menu, practice, words, import, reminder, vocabulary, tasks/stats for RU/EN/JA; add JSON-based i18n helper\n\nfeat(lang): support learning/translation languages across AI flows; hide translations with buttons; store examples per lang\n\nfeat(vocab): add source_lang and translation_lang to Vocabulary, unique constraint (user_id, source_lang, word_original); filter /vocabulary by user.learning_language\n\nchore(migrations): add Alembic setup + migration to add vocab lang columns; env.py reads app settings and supports asyncpg URLs\n\nfix(words/import): pass learning_lang + translation_lang everywhere; fix menu themes generation\n\nfeat(settings): add learning language selector; update main menu on language change

services/user_service.py

@@ -95,3 +95,22 @@ class UserService:
         if user:
             user.language_interface = language
             await session.commit()
+
+    @staticmethod
+    async def update_user_learning_language(session: AsyncSession, user_id: int, language: str):
+        """
+        Обновить язык изучения пользователя
+
+        Args:
+            session: Сессия базы данных
+            user_id: ID пользователя
+            language: Новый язык изучения (ISO2)
+        """
+        result = await session.execute(
+            select(User).where(User.id == user_id)
+        )
+        user = result.scalar_one_or_none()
+
+        if user:
+            user.learning_language = language
+            await session.commit()