Web: date picker commits on leave, close day context menu on event click

- Date picker: clicking a day only selects it now; the choice is committed
  when you leave the picker (click outside) or press Save — for both date and
  datetime modes (previously datetime discarded on click-away, and date
  committed instantly on click, neither of which was wanted).
- The day right-click context menu ("Neuen Termin erstellen") now closes when
  an event popup opens (the event row stops propagation, so its own
  outside-click closer never fired).
- version v47 -> v48.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/js/calendar.js

@@ -1373,6 +1373,9 @@ function showDayContextMenu(date, mouseEvent) {
 
 // ── Event Popup ───────────────────────────────────────────
 function showEventPopup(ev, anchor) {
+  // The event row stops click propagation, so the day context menu's own
+  // outside-click closer never fires — remove it explicitly here.
+  document.querySelectorAll('.cal-context-menu').forEach(m => m.remove());
   const popup = document.getElementById('popup-event');
   document.getElementById('popup-copy-menu').classList.add('hidden');
   popup.classList.remove('hidden');