Add referee assignment/eligibility system, team bulk-add, member Groups, and referee management dashboard with PDF export

Builds the referee workflow end to end: club-defined RefereeLevel/RefereeProfile
eligibility tied to teams, EventReferee assignment (member or external, with
fee/km payment tracking), an admin dashboard with KPI tiles, date-grouped game
tiles and range filters, and a downloadable payment form PDF modeled on the
club's existing paper document (using Club.legal_name when set). Also lands
team roster bulk-add, member mass-upload with family linking, and the
members.Group model, developed alongside this work.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

management/pdf.py

@@ -28,3 +28,8 @@ def render_pdf(html: str) -> bytes:
 def membership_list_pdf(context: dict) -> bytes:
     html = render_to_string("management/membership_list_pdf.html", context)
     return render_pdf(html)
+
+
+def event_referee_form_pdf(context: dict) -> bytes:
+    html = render_to_string("management/event_referee_form_pdf.html", context)
+    return render_pdf(html)