Three Android UX fixes reported from on-device testing:
1. A calendar shared with the user now shows read-only affordances: parse the
server's new read_only flag on events, show a lock icon in the filter sheet,
and exclude read-only shared calendars from the event editor's calendar
picker (getWritableCalendars) so saves no longer 403. The calendar's display
name (owner's name) comes from the server.
2. (server-side) group event name prefix removed — no client change needed.
3. Move the personal/group view switcher out of the crowded top bar into the
burger MenuSheet as a "group view" section (personal + each group with a
check mark), mirroring iOS. The GroupSwitcher pill and its top-bar wiring are
gone; the active-group banner stays.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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