feat: JLPT levels for Japanese, custom practice scenarios, UI improvements

- Add separate level systems: CEFR (A1-C2) for European languages, JLPT (N5-N1) for Japanese
- Store levels per language in new `levels_by_language` JSON field
- Add custom scenario option in AI practice mode
- Show action buttons after practice ends (new dialogue, tasks, words)
- Fix level display across all handlers to use correct level system
- Add Alembic migration for levels_by_language field
- Update all locale files (ru, en, ja) with new keys

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

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

bot/handlers/import_text.py

@@ -9,7 +9,8 @@ from database.models import WordSource
 from services.user_service import UserService
 from services.vocabulary_service import VocabularyService
 from services.ai_service import ai_service
-from utils.i18n import t
+from utils.i18n import t, get_user_lang
+from utils.levels import get_user_level_for_language
 
 router = Router()
 
@@ -44,7 +45,10 @@ async def cmd_import(message: Message, state: FSMContext):
 async def cancel_import(message: Message, state: FSMContext):
     """Отмена импорта"""
     await state.clear()
-    await message.answer("❌ Импорт отменён.")
+    async with async_session_maker() as session:
+        user = await UserService.get_user_by_telegram_id(session, message.from_user.id)
+    lang = get_user_lang(user)
+    await message.answer(t(lang, 'import_extra.cancelled'))
 
 
 @router.message(ImportStates.waiting_for_text)
@@ -52,12 +56,16 @@ async def process_text(message: Message, state: FSMContext):
     """Обработка текста от пользователя"""
     text = message.text.strip()
 
+    async with async_session_maker() as session:
+        user = await UserService.get_user_by_telegram_id(session, message.from_user.id)
+    lang = get_user_lang(user)
+
     if len(text) < 50:
-        await message.answer(t('ru', 'import.too_short'))
+        await message.answer(t(lang, 'import.too_short'))
         return
 
     if len(text) > 3000:
-        await message.answer(t('ru', 'import.too_long'))
+        await message.answer(t(lang, 'import.too_long'))
         return
 
     async with async_session_maker() as session:
@@ -67,9 +75,10 @@ async def process_text(message: Message, state: FSMContext):
         processing_msg = await message.answer(t(user.language_interface or 'ru', 'import.processing'))
 
         # Извлекаем слова через AI
+        current_level = get_user_level_for_language(user)
         words = await ai_service.extract_words_from_text(
             text=text,
-            level=user.level.value,
+            level=current_level,
             max_words=15,
             learning_lang=user.learning_language,
             translation_lang=user.language_interface,
@@ -87,7 +96,7 @@ async def process_text(message: Message, state: FSMContext):
             words=words,
             user_id=user.id,
             original_text=text,
-            level=user.level.name
+            level=current_level
         )
         await state.set_state(ImportStates.viewing_words)