Fix email masking: show at least half the local part (min 4 chars)

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

app/Services/TelegramBotService.php

@@ -1186,8 +1186,9 @@ class TelegramBotService
     private function maskEmail(string $email): string
     {
         [$local, $domain] = explode('@', $email, 2);
-        $visible = mb_substr($local, 0, min(3, mb_strlen($local)));
-        return $visible . str_repeat('*', max(0, mb_strlen($local) - 3)) . '@' . $domain;
+        $len     = mb_strlen($local);
+        $visible = max(4, (int) ceil($len / 2)); // muestra la mitad, mínimo 4 caracteres
+        return mb_substr($local, 0, min($visible, $len)) . str_repeat('*', max(0, $len - $visible)) . '@' . $domain;
     }
 
     private function createMPPreference(string $titulo, int $valor, string $ref): ?string