Add billing-ending banner, events CRUD, RBIHF import, public API, team photos, and sponsors

A large batch of club-management features built up over one session:

- Club dashboard banner warning admins 1 month before billing ends
- Full Events/EventSeries CRUD (recurrence builder, occurrence lifecycle,
  per-team permissions), with match->game rename and game-specific fields
  (score, competition, live status, external game ID)
- Django-admin competition dropdown, gated per-club by feature flag
- Auto-import of RBIHF fixtures (scrape -> diff -> preview -> confirm),
  with location/opponent dropdowns suggested from existing club data
- Feature-flag-gated Shop/Forms nav sections, reusing the same flag
  machinery for the RBIHF import button
- Team roster now scoped to members active this season or next, sorted and
  grouped by position
- Club sport type (ice hockey / other), shown in the control panel's club
  subtitle
- Per-season team photo upload from the team page
- New public read-only API (Django Ninja) at /api/v1/: news, team rosters,
  upcoming/live/per-team games, and sponsors -- auto-documented via Swagger
  UI, CORS-enabled for a club's own external website
- Club sponsors: admin-only CRUD (logo, URL, active date window) plus a
  date-windowed, optionally randomized API endpoint
- Assorted fixes: NullBooleanField dropdown rendering, cross-club event
  validation timing, searchable-select chip placement, btn-neutral ->
  default button style sweep, calendar-month chart windows

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01R1gj3J1QPfP38XWpnpbFpy

club/tests.py

@@ -20,7 +20,7 @@ from events.models import Event
 from members.models import Family, FamilyMembership, Member
 from teams.models import Position, StaffAssignment, Team, TeamMembership
 
-from .models import Club, ClubMembership, ClubRole, FeePayment, Season, club_logo_path
+from .models import Club, ClubMembership, ClubRole, FeePayment, Season, Sponsor, club_logo_path
 from .services.access import (
     COACH_MANAGER,
     can_edit_event,
@@ -464,6 +464,56 @@ class SeasonGetCurrentTests(TestCase):
             Season.get_current(datetime.date(2026, 12, 25))
 
 
+class SeasonNextAfterTests(TestCase):
+    def setUp(self):
+        self.club = Club.objects.create(name="Ajax United", slug="ajax-united")
+        self.current = Season.objects.create(club=self.club, start_date=datetime.date(2026, 8, 1), end_date=datetime.date(2027, 5, 31))
+        self.next_season = Season.objects.create(club=self.club, start_date=datetime.date(2027, 8, 1), end_date=datetime.date(2028, 5, 31))
+
+    def test_returns_the_soonest_season_starting_after_the_date(self):
+        self.assertEqual(Season.next_after(self.club, datetime.date(2026, 12, 25)), self.next_season)
+
+    def test_returns_none_when_there_is_no_later_season(self):
+        self.assertIsNone(Season.next_after(self.club, datetime.date(2027, 12, 25)))
+
+    def test_is_scoped_to_the_given_club(self):
+        other = Club.objects.create(name="Rival FC", slug="rival-fc")
+        Season.objects.create(club=other, start_date=datetime.date(2027, 8, 1), end_date=datetime.date(2028, 5, 31))
+
+        self.assertEqual(Season.next_after(other, datetime.date(2026, 12, 25)).club, other)
+
+
+class SponsorModelTests(TestCase):
+    def setUp(self):
+        self.club = Club.objects.create(name="Ajax United", slug="ajax-united")
+
+    def test_str_returns_name(self):
+        sponsor = Sponsor.objects.create(club=self.club, name="Acme Corp", start_date=datetime.date(2026, 1, 1))
+
+        self.assertEqual(str(sponsor), "Acme Corp")
+
+    def test_a_blank_end_date_is_valid(self):
+        sponsor = Sponsor(club=self.club, name="Acme Corp", start_date=datetime.date(2026, 1, 1))
+        sponsor.full_clean()
+
+    def test_an_end_date_on_the_same_day_as_start_is_valid(self):
+        sponsor = Sponsor(club=self.club, name="Acme Corp", start_date=datetime.date(2026, 1, 1), end_date=datetime.date(2026, 1, 1))
+        sponsor.full_clean()
+
+    def test_an_end_date_before_start_is_rejected(self):
+        sponsor = Sponsor(club=self.club, name="Acme Corp", start_date=datetime.date(2026, 6, 1), end_date=datetime.date(2026, 1, 1))
+
+        with self.assertRaises(ValidationError) as ctx:
+            sponsor.full_clean()
+        self.assertIn("end_date", ctx.exception.error_dict)
+
+    def test_sponsors_are_ordered_by_name(self):
+        Sponsor.objects.create(club=self.club, name="Zulu Corp", start_date=datetime.date(2026, 1, 1))
+        Sponsor.objects.create(club=self.club, name="Acme Corp", start_date=datetime.date(2026, 1, 1))
+
+        self.assertEqual(list(Sponsor.objects.values_list("name", flat=True)), ["Acme Corp", "Zulu Corp"])
+
+
 class AdminRegistrationSmokeTests(TestCase):
     """Every registered model across all apps must have a working admin: load
     each changelist and add page to catch bad list_display / search_fields /