Add alias SMTP/Sieve resolution, debug logging, and exclude aliases from switcher

SMTP and Sieve hooks follow parent_id to resolve alias config from parent
account. Aliases excluded from account switcher dropdown and background
mail checker. Debug logging behind ident_switch.debug config flag.
Fix double ssl:// prefix in switch_account host parsing.

config.inc.php.dist

@@ -92,3 +92,10 @@ $config['ident_switch.hide_notifier_warning'] = false;
  * Default: false (all domains allowed).
  */
 $config['ident_switch.preconfig_only'] = false;
+
+/*
+ * Enable debug logging to logs/ident_switch.log.
+ * Useful for troubleshooting SMTP/Sieve routing and alias resolution.
+ * Default: false.
+ */
+$config['ident_switch.debug'] = false;