calendar: include Bis: in the appointment-create template

CalDavSync already reads **Bis:** out of the body on push (and writes
it on pull), but the in-app template used when the user clicks a
calendar day to create an appointment didn't offer the field —
forcing the user to type the marker from scratch for multi-day or
ranged events. Drop it in next to **Zeit:** so the round-trip is
symmetric.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

config.php

@@ -1,7 +1,7 @@
 <?php
 
 define('APP_NAME', 'hyprcrd');
-define('APP_VERSION', '1.9.7');
+define('APP_VERSION', '1.9.8');
 
 // Database path — writable directory, outside webroot
 // DB_PATH / UPLOAD_DIR can be pre-defined by the Electron router for app isolation