Fix double delete confirm, inline place name editing, preserve assignments on trip extend

- Replace double browser confirm() with single custom ConfirmDialog for place deletion
- Add inline name editing via double-click in PlaceInspector
- Rewrite generateDays() to preserve existing days/assignments when extending trips
- Use UTC date math to avoid timezone-related day count errors
- Add missing collab.chat.emptyDesc translation (en/de)

client/src/components/Planner/PlacesSidebar.jsx

@@ -146,7 +146,7 @@ export default function PlacesSidebar({
                   place.website && { label: t('inspector.website'), icon: ExternalLink, onClick: () => window.open(place.website, '_blank') },
                   (place.lat && place.lng) && { label: 'Google Maps', icon: Navigation, onClick: () => window.open(`https://www.google.com/maps/search/?api=1&query=${place.lat},${place.lng}`, '_blank') },
                   { divider: true },
-                  onDeletePlace && { label: t('common.delete'), icon: Trash2, danger: true, onClick: () => { if (confirm(t('trip.confirm.deletePlace'))) onDeletePlace(place.id) } },
+                  onDeletePlace && { label: t('common.delete'), icon: Trash2, danger: true, onClick: () => onDeletePlace(place.id) },
                 ])}
                 style={{
                   display: 'flex', alignItems: 'center', gap: 10,