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>

electron/package.json

@@ -1,6 +1,6 @@
 {
   "name": "hyprcrd",
-  "version": "1.9.7",
+  "version": "1.9.8",
   "description": "hyprcrd — self-hosted card manager",
   "main": "main.js",
   "scripts": {