feat: Add SSH public key storage for users

- Add ssh_public_key column to User model for storing SSH keys
- Add database migration for ssh_public_key column
- Add SSH key section in user profile settings with validation
- Auto-inject user's SSH key when deploying VMs from templates
- Auto-inject user's SSH key when creating LXC containers
- Support for both regular and smart LXC creation endpoints
- Add i18n translations for SSH key UI (ru/en)
- Validate SSH key format (ssh-rsa, ssh-ed25519, ecdsa-sha2, ssh-dss)

Users can now save their SSH public key in Settings -> Account,
and it will be automatically added to any VM or LXC container
they create, enabling passwordless SSH access.

backend/app/static/js/i18n.js

@@ -41,6 +41,11 @@ const translations = {
         no_updates: "Установлена последняя версия",
         update_warning: "Панель будет недоступна во время обновления",
         updating_system: "Обновление системы...",
+        
+        // SSH Keys
+        ssh_key_saved: "SSH ключ успешно сохранён",
+        error_saving_ssh_key: "Ошибка сохранения SSH ключа",
+        invalid_ssh_key_format: "Неверный формат SSH ключа",
     },
     
     en: {
@@ -80,6 +85,11 @@ const translations = {
         no_updates: "You have the latest version",
         update_warning: "Panel will be unavailable during update",
         updating_system: "Updating system...",
+        
+        // SSH Keys
+        ssh_key_saved: "SSH key saved successfully",
+        error_saving_ssh_key: "Error saving SSH key",
+        invalid_ssh_key_format: "Invalid SSH key format",
     }
 };