fix(sync): resolve iCloud Calendar sync FOREIGN KEY crash and sync all calendars

The Apple Calendar sync hardcoded created_by=1 which fails when no user
with ID 1 exists, causing every single event import to fail silently.
Now dynamically resolves the first available user. Also syncs all
calendars instead of only the first one, adds the missing cfgDel helper,
and gracefully skips unreachable calendars.

Fixes #4

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

package.json

@@ -1,6 +1,6 @@
 {
   "name": "oikos",
-  "version": "0.5.4",
+  "version": "0.5.5",
   "description": "Selbstgehosteter Familienplaner — Kalender, Aufgaben, Einkauf, Essensplan, Budget und mehr. Privat, offen, ohne Abo.",
   "main": "server/index.js",
   "engines": {