fix(web): can't edit calendars shared with me; struck-pencil read-only marker

- Sidebar: don't start an inline rename on a calendar I don't own (owned=false)
  — the save would only 403. Colour picker was already gated.
- Sidebar: show a struck-through pencil icon on read-only shared calendars.

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 = 'v71';
+export const APP_VERSION = 'v72';