Add password validation with i18n support and GitHub button improvements

- Add password field to UserUpdate schema for password change on edit
- Implement password validation in update_user endpoint
- Add i18n translations for password validation errors (ru/en)
- Update SecurityService.validate_password to support language parameter
- Add GitHub icon and repository name 'pvemanager' to header button
- Fix internal server error when updating user password
- Clean up hardcoded translations in frontend

.env.example

@@ -4,3 +4,9 @@ POSTGRES_PASSWORD=serverpanel_secure_password
 # Timezone
 TZ=Asia/Tashkent
 TIMEZONE=Asia/Tashkent
+
+# Update Check Configuration (for private repositories)
+# Set to true to disable update checks
+DISABLE_UPDATE_CHECK=true
+# GitHub token for private repositories (optional, get at: https://github.com/settings/tokens)
+GITHUB_TOKEN=