- Month view: Replaced day-strip+events-area with full-height column
divs (.month-col) so borders extend the full row height and clicking
anywhere in a day column (including below events) navigates to day view.
Events overlay uses pointer-events:none (pass-through) while span bars
and +N-more labels stay pointer-events:all.
- Scroll navigation: Changed wheel handler from 80ms debounce to 500ms
leading-edge throttle — one navigation per trackpad gesture.
- Custom date/time picker (date-picker.js): Dark calendar grid with
prev/next navigation, today/selected highlighting, and a CSS
scroll-snap time scroller (hours 0-23, minutes 0-59) matching the
app's primary color. Language-aware (month names, day headers via t()).
- Event modal datetime inputs replaced with hidden inputs + .dt-display
click targets that open the custom picker. setDtValue() helper keeps
hidden input and display label in sync.
