feat(events): event owner and cross-club validation

Add Event.created_by (the owner, used later by the access service to let an
event's creator edit it).

Validate that an event's season/location/opponent — and an EventSeries'
location/opponent — belong to the event's club. The teams M2M cannot be checked
in clean() (M2M rows are written after save), so an m2m_changed pre_add receiver
rejects teams from another club.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

events/models.py

@@ -2,7 +2,7 @@ from django.db import models
 from django.utils.translation import gettext_lazy as _
 
 from club.models import Season
-from clubmanager.base import ClubScopedModel, UUIDModel
+from clubmanager.base import ClubScopedModel, UUIDModel, validate_club_scope
 from members.models import Member
 from teams.models import Team
 
@@ -64,6 +64,7 @@ class Event(ClubScopedModel):
 
     location = models.ForeignKey(Location, on_delete=models.SET_NULL, related_name="events", null=True, blank=True, verbose_name=_("location"))
     opponent = models.ForeignKey(Opponent, on_delete=models.SET_NULL, related_name="events", null=True, blank=True, verbose_name=_("opponent"))
+    created_by = models.ForeignKey(Member, on_delete=models.SET_NULL, related_name="created_events", null=True, blank=True, verbose_name=_("created by"))
 
     class Meta:
         verbose_name = _("event")
@@ -73,6 +74,9 @@ class Event(ClubScopedModel):
     def __str__(self):
         return self.title
 
+    def clean(self):
+        validate_club_scope(self, self.club_id, same_club_fields=("season", "location", "opponent"))
+
 
 class EventSeries(ClubScopedModel):
     """A recurring event definition that materialises concrete Event rows."""
@@ -103,6 +107,9 @@ class EventSeries(ClubScopedModel):
     def __str__(self):
         return self.title
 
+    def clean(self):
+        validate_club_scope(self, self.club_id, same_club_fields=("location", "opponent"))
+
 
 class Attendance(UUIDModel):
     class AttendanceStatus(models.TextChoices):