Tasks with due dates now appear directly on the weekly calendar view,
similar to Google Calendar. Removes the tab bar UI in favor of a
unified calendar view where todos are visually distinct (secondary
color, checkbox prefix) and clickable to toggle completion.

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

Add full VTODO/task management via Evolution Data Server Python scripts
(list, create, complete/uncomplete, delete) and integrate into the panel
with a Calendar/Tasks tab bar, task list view with priority indicators,
due date display, and a create task dialog.

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