Notifications: summarize multi-person names in the calendar event title

A recognition/training notification for many people prefixed the calendar title
with the entire roster ("Name1, Name2, ... , Name20: description"), burying the
description. to_calendar_event now shows "First Person +N" when more than one
person is listed; single-person titles are unchanged and the detail popup still
shows the full employeename. Fixes the cluttered month grid, especially after
the loader began resolving employee SSOs to names.

31 notification/calendar tests pass; naming green.

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

plugins/notifications/models/notification.py

@@ -159,11 +159,17 @@ class Notification(db.Model):
         color = color_aliases.get(raw_color, raw_color if raw_color.startswith('#') else '#14abef')
         show_photo = bool(ntype and getattr(ntype, 'showemployeephoto', False))
 
-        # Employee-photo types prefix the card with the person's name/SSO.
+        # Employee-photo types prefix the card with the person's name/SSO. A
+        # multi-person recognition/training lists many people, so summarize as
+        # "First Person +N" to keep the calendar title short (the detail popup
+        # still shows the full employeename).
         title = self.title
         if show_photo:
             employee_display = self.employeename or self.employeesso
             if employee_display:
+                people = [p.strip() for p in employee_display.split(',') if p.strip()]
+                if len(people) > 1:
+                    employee_display = f"{people[0]} +{len(people) - 1}"
                 title = f"{employee_display}: {title}"
 
         return {