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

api/urls.py

@@ -0,0 +1,28 @@
+"""The public read-only API -- see ARCHITECTURE.md and the plan this shipped
+under. Mounted at /api/v1/ (rosterchief/urls.py), club-scoped by the same
+subdomain-based tenant resolution every other view uses
+(club.tenancy.ClubTenantMiddleware sets request.club before this ever runs).
+
+Each domain app owns its own router and schemas (news/api.py, teams/api.py,
+events/api.py) -- this module only wires them together, same reasoning as
+management/controlpanel never owning domain logic themselves.
+"""
+
+from ninja import NinjaAPI
+
+from club.api import router as club_router
+from events.api import router as events_router
+from news.api import router as news_router
+from teams.api import router as teams_router
+
+api = NinjaAPI(
+    title="RosterChief public API",
+    version="1.0.0",
+    description="Public, read-only data for a club's own external website: news, team rosters, fixtures, and sponsors.",
+    urls_namespace="api",
+)
+
+api.add_router("/news", news_router)
+api.add_router("/teams", teams_router)
+api.add_router("/", events_router)
+api.add_router("/sponsors", club_router)