fix(web): bind UI handlers before first fetch so a data error can't kill the UI

initCalendar() awaited fetchAndRender() BEFORE binding the topbar/settings/menu
handlers, so any error from /caldav/events (e.g. a transient 500) threw out of
init and left the buttons dead — the reported "settings won't open". Same root
cause as the reload-logout bug: app wiring must not depend on event data loading.

Bind all handlers first, then fetch inside try/catch (errors are logged + shown
as a toast, no longer fatal). v75.

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 = 'v74';
+export const APP_VERSION = 'v75';