Add calendar sync: a combined iCal subscription feed per account

New mobile:calendar_feed (/app/calendar/<token>.ics) -- a standard
webcal-style subscription feed calendar apps can poll, so a family's
schedule shows up in Apple/Google/Outlook Calendar alongside everything
else. Token-authenticated rather than session-authenticated (calendar
apps can't do interactive login); CalendarFeedToken is deliberately not
club-scoped, since the same token works under whichever club subdomain
the request is fetched from -- an account active in more than one club
needs only the one link.

Combined across every managed person (their name goes in the event
title when there's more than one), every event they're invited to
regardless of RSVP status, not capped to Calendar's own 2-week window --
a synced calendar app is exactly where someone wants the whole season
visible. A cancelled event stays in the feed as STATUS:CANCELLED rather
than disappearing, so it's removed properly on the subscriber's next
refresh instead of just vanishing.

New mobile:calendar_feed_settings (linked from Me) shows the webcal://
and https:// links plus a "reset my calendar link" action that
immediately invalidates the old one. Uses the icalendar package for
RFC 5545 generation rather than hand-rolling escaping/line-folding.

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

mobile/views.py

@@ -36,7 +36,8 @@ from teams.models import TeamMembership
 
 from .forms import MemberProfileForm
 from .mixins import PersonScopeMixin
-from .models import PushSubscription
+from .models import CalendarFeedToken, PushSubscription
+from .services.calendar_feed import build_feed
 from .services.icons import render_fallback_icon
 
 
@@ -121,6 +122,54 @@ class PushSubscribeView(LoginRequiredMixin, ClubScopedPublicMixin, View):
         return JsonResponse({"status": "ok"})
 
 
+class CalendarFeedView(ClubScopedPublicMixin, View):
+    """The .ics subscription feed a calendar app polls -- URL-token
+    authenticated, not LoginRequiredMixin (a calendar app can't do
+    interactive login). See mobile.services.calendar_feed.build_feed for the
+    feed's own shape/scope, and CalendarFeedToken's own docstring for why one
+    token covers every club the account belongs to."""
+
+    def get(self, request, token):
+        feed_token = get_object_or_404(CalendarFeedToken.objects.select_related("user"), token=token)
+        me = Member.objects.filter(user=feed_token.user).first()
+        people = []
+        if me is not None:
+            children = Member.objects.filter(
+                family_memberships__role=FamilyMembership.FamilyRole.CHILD,
+                family_memberships__family__memberships__member=me,
+                family_memberships__family__memberships__role__in=[FamilyMembership.FamilyRole.PARENT, FamilyMembership.FamilyRole.GUARDIAN],
+                member_of__club=request.club,
+            ).distinct()
+            people = [me, *children]
+
+        feed = build_feed(request.club, people)
+        return HttpResponse(feed, content_type="text/calendar; charset=utf-8")
+
+
+class CalendarFeedSettingsView(PersonScopeMixin, LoginRequiredMixin, TemplateView):
+    """M5's "Calendar sync" row -- the webcal://.../https:// subscription
+    links for this account's combined feed, plus a reset action that
+    immediately invalidates the old URL (e.g. a link shared/leaked by
+    accident)."""
+
+    template_name = "mobile/calendar_feed_settings.html"
+    screen_title = _("Calendar sync")
+    active_tab = "me"
+
+    def get_context_data(self, **kwargs):
+        feed_token, _created = CalendarFeedToken.objects.get_or_create(user=self.request.user)
+        feed_url = self.request.build_absolute_uri(reverse("mobile:calendar_feed", kwargs={"token": feed_token.token}))
+        return super().get_context_data(feed_url=feed_url, webcal_url=feed_url.replace("https://", "webcal://", 1).replace("http://", "webcal://", 1), **kwargs)
+
+    def post(self, request, *args, **kwargs):
+        feed_token, _created = CalendarFeedToken.objects.get_or_create(user=request.user)
+        feed_token.regenerate()
+        title = _("Calendar link reset")
+        body = _("Your old calendar link no longer works. Re-subscribe using the new one below.")
+        notify(request, f"s|{title}|{body}")
+        return HttpResponseRedirect(reverse("mobile:calendar_feed_settings"))
+
+
 class HomeView(PersonScopeMixin, LoginRequiredMixin, TemplateView):
     """M1 -- design_handoff_rosterchief_platform/README.md's M1 section: a
     hero card for the soonest upcoming event across everyone currently in