feat: restructure menu and add file import

- Consolidate "Add word" menu with submenu (Manual, Thematic, Import)
- Add file import support (.txt, .md) with AI batch translation
- Add vocabulary pagination with navigation buttons
- Add "Add word" button in tasks for new words mode
- Fix undefined variables bug in vocabulary confirm handler
- Add localization keys for add_menu in ru/en/ja

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

bot/handlers/words.py

@@ -45,6 +45,13 @@ async def cmd_words(message: Message, state: FSMContext):
             return
 
         theme = command_parts[1].strip()
+        await generate_words_for_theme(message, state, theme, message.from_user.id)
+
+
+async def generate_words_for_theme(message: Message, state: FSMContext, theme: str, user_id: int):
+    """Генерация слов по теме (вызывается из cmd_words и callback)"""
+    async with async_session_maker() as session:
+        user = await UserService.get_user_by_telegram_id(session, user_id)
 
         # Показываем индикатор генерации
         lang = user.language_interface or 'ru'