Fix PHP 8.5 deprecation of PDO::sqliteCreateFunction()

PHP 8.5 deprecated PDO::sqliteCreateFunction() in favor of
Pdo\Sqlite::createFunction(). Use the new method on PHP 8.0+
where it is available, falling back to the old method for
older versions.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: superdav42

src/db.php

@@ -152,7 +152,11 @@ public function __construct($pdo)
                 wp_die('Database is not initialized.', 'Database Error');
             }
             foreach ($this->functions as $f => $t) {
-                $pdo->sqliteCreateFunction($f, [$this, $t]);
+                if (PHP_VERSION_ID >= 80000) {
+                    $pdo->createFunction($f, [$this, $t]);
+                } else {
+                    $pdo->sqliteCreateFunction($f, [$this, $t]);
+                }
             }
         }