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

pyproject.toml

@@ -3,11 +3,13 @@ name = "rosterchief"
 version = "0.1.0"
 requires-python = ">=3.14"
 dependencies = [
+    "beautifulsoup4>=4.15.0",
     "dj-database-url>=3.1.2",
     "django>=6.0.6",
     "django-allauth[mfa]>=65.18.0",
     "django-countries>=9.0.0",
     "django-lucide",
+    "django-ninja>=1.6.2",
     "django-phonenumber-field[phonenumbers]>=8.4.0",
     "django-redis>=7.0.0",
     "django-storages[s3]>=1.14.6",
@@ -18,6 +20,7 @@ dependencies = [
     "psycopg[binary]>=3.3.4",
     "python-dateutil>=2.9.0.post0",
     "python-decouple>=3.8",
+    "requests>=2.34.2",
     "weasyprint>=69.0",
     "whitenoise>=6.12.0",
 ]
@@ -58,7 +61,7 @@ ignore = [
 
 [tool.ruff.lint.isort]
 known-first-party = [
-    "billing", "authentication", "club", "members", "teams", "events", "formbuilder", "shop", "controlpanel", "management", "news", "pages", "home", "search", "rosterchief"]
+    "api", "billing", "authentication", "club", "members", "teams", "events", "formbuilder", "shop", "controlpanel", "management", "news", "pages", "home", "search", "rosterchief"]
 
 [tool.uv.sources]
 django-lucide = { git = "https://github.com/bsiebens/lucide" }