feat(web): show shared calendars under the owner's name

A calendar shared with another person now appears to the recipient under the
OWNER's name (Guido's "Persönlich" shows as "Guido"), matching the iOS filter
sheet. The original calendar name moves to the sub-label / settings source
column so it stays identifiable. Sidebar list + settings table.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/js/version.js

@@ -1,2 +1,2 @@
 // Increment APP_VERSION with every code change
-export const APP_VERSION = 'v69';
+export const APP_VERSION = 'v70';