Add user isolation mode and transfer features

Introduces user isolation mode, allowing domains, groups, and tags to be visible only to their owners when enabled. Adds user_id fields to domains and notification_groups, updates models and controllers for isolation-aware queries, and provides admin UI and endpoints for transferring domains and groups between users (single and bulk). Includes migration, settings UI, and routes for toggling isolation mode and handling data migration.

app/Controllers/InstallerController.php

@@ -49,6 +49,7 @@ class InstallerController extends Controller
             '015_create_error_logs_table.sql',
             '016_add_tags_to_domains.sql',
             '017_add_two_factor_authentication.sql',
+            '018_add_user_isolation.sql',
         ];
         
         try {
@@ -268,6 +269,8 @@ class InstallerController extends Controller
                     '014_add_captcha_settings.sql',
                     '015_create_error_logs_table.sql',
                     '016_add_tags_to_domains.sql',
+                    '017_add_two_factor_authentication.sql',
+                    '018_add_user_isolation.sql',
                 ];
                 
                 $stmt = $pdo->prepare("INSERT INTO migrations (migration) VALUES (?) ON DUPLICATE KEY UPDATE migration=migration");