fix(sidebar): absolute-position action buttons to prevent name truncation

Buttons (.cal-item-remove, .cal-item-bell) are now position:absolute so
they never participate in flex layout — names get full available width at
all times. Buttons fade in over the right edge of the item on hover with
no layout shift and no row-height change.

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

frontend/js/version.js

@@ -1,2 +1,2 @@
 // Increment APP_VERSION with every code change
-export const APP_VERSION = 'v56';
+export const APP_VERSION = 'v57';