Pixmenia v23 Admin Settings + Assets Protection

- Protected admin/payment/settings data in pixboost_app/sql/database.sql
- Added sql/v23_preserve_admin_settings.sql
- Added settings backup/restore functions to includes/database_guard.php
- Added settings backup/restore functions to pixboost_app/admin/database_guard.php
- Added settings backup/restore functions to pixboost_app/includes/database_guard.php
- Added settings backup/restore buttons to pixboost_app/admin/post_update_repair.php

PHP Syntax: pixboost_app/admin/database_guard.php: PHP Parse error:  syntax error, unexpected token "function", expecting "," or ";" in /mnt/data/pix_v23_settings_guard/pixboost_app/admin/database_guard.php on line 160
SQL Safety: Protected table insert still present in sql/v19_persistent_assets.sql: settings

Protected: admin settings, logo, favicon, Stripe, PayPal, Resend, SEO, colors, packages, customer image links.