fix: add unicode flag to named param regex for ö/ä chars

Column name yhteyshenkilö contains ö which \w doesn't match
without the /u flag. This caused SQL syntax errors.

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

db.php

@@ -35,7 +35,7 @@ function _dbRun(string $sql, array $params = []): mysqli_stmt {
     // Muunna nimetyt parametrit (:name) positiivisiksi (?)
     if (!empty($params) && !array_is_list($params)) {
         $ordered = [];
-        $sql = preg_replace_callback('/:(\w+)/', function($m) use ($params, &$ordered) {
+        $sql = preg_replace_callback('/:(\w+)/u', function($m) use ($params, &$ordered) {
             $key = $m[1];
             $ordered[] = array_key_exists($key, $params) ? $params[$key] : null;
             return '?';