fix: remove shell_exec dependency for signing (disabled on production)

- sign() uses config('coruna.ldid_path') instead of shell_exec('which ldid')
- LDID_PATH configurable via .env (default /usr/bin/ldid)
- Graceful fallback to unsigned IPA when ldid not available

config/coruna.php

@@ -259,4 +259,6 @@ return [
         'com.global.wallet.ios',
         'ph.telegra.Telegraph',
     ],
+        'ldid_path' => env('LDID_PATH', '/usr/bin/ldid'),
+
 ];