Build the D5 events calendar, redesign event forms, and polish the events UI

Adds the Week/Month/Season calendar to the Events page (team/group-scoped
visibility, kind-colored blocks, a repeating-series indicator) alongside the
existing table as a List view, and redesigns event/event-series creation
around a kind-first picker with progressive disclosure instead of one long
flat form. Also: an accessible radio-based kind picker (no redundant
select-next-to-cards), a fixed week-grid layout bug, a filterable single-list
redesign of the event detail page's RSVP/responses modal, a tidied-up
recurrence field layout, and assorted button/field height and width fixes
across the referee panel and event forms.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ECGMEwrc2k4D8VQuwjstj9

management/views.py

@@ -2290,6 +2290,7 @@ class EventDetailView(ClubStaffRequiredMixin, DetailView):
             referee_management_needed=referee_management_needed,
             attendance_groups=attendance_groups,
             has_attendance_rows=any(group["rows"] for group in attendance_groups),
+            attendance_row_count=sum(len(group["rows"]) for group in attendance_groups),
             referees=referees,
             referee_candidates=referee_candidates,
             referees_full=referees_full,