Add custom emoji mapping system for premium emoji support

- Create emoji_mappings table to store emoji->emoji_id mappings
- Add EmojiMappingService for managing emoji registration and replacement
- Add admin emoji handlers (/add_emoji, /my_emojis, /delete_emoji, /all_emojis)
- Create emoji message helper for automatic emoji processing
- Add Alembic migration for emoji_mappings table
- Integrate emoji router into main dispatcher
- Add comprehensive documentation (EMOJI_SYSTEM.md)
- Fix migration chain issue with merge_migration

Features:
- Admins can register premium emojis via /add_emoji command
- Automatic emoji->emoji_id replacement before sending messages
- Per-admin unique constraint on emoji registration
- Track last used timestamp for analytics
- Bulk operations support

main.py

@@ -30,6 +30,7 @@ from src.handlers.account_handlers import account_router
 from src.handlers.message_management import message_admin_router
 from src.handlers.p2p_chat import router as p2p_chat_router
 from src.handlers.help_handlers import router as help_router
+from src.handlers.admin_emoji_handlers import router as admin_emoji_router
 
 # Настройка логирования
 logging.basicConfig(
@@ -289,6 +290,7 @@ async def main():
     
     # 2. Специфичные роутеры
     dp.include_router(message_admin_router)  # Управление сообщениями администратором
+    dp.include_router(admin_emoji_router)  # Управление кастомными эмодзи
     dp.include_router(admin_router)  # Админ панель - самая высокая специфичность
     dp.include_router(registration_router)  # Регистрация
     dp.include_router(admin_account_router)  # Админские команды счетов