Remove OnboardingRequirement.order; restrict checklist actions to admin/MEMBER_ADMIN

Every active requirement blocks equally and there's no set order to complete
them in, so the configurable "order" field (and its ordering-by-number) is
gone -- requirements list alphabetically now, both in the admin UI and the
Onboarding requirements settings page.

Also closes a real permission gap found while checking this: marking a
checklist item complete, bypassing it, or reopening it (management/views.py's
MemberRequirementCompleteView/BypassView/IncompleteView) was open to *any*
staff member with page access, not just admin/MEMBER_ADMIN, despite the
member detail page's own Documents card implying otherwise. Switched all
three to MemberAdminRequiredMixin and hid the corresponding buttons/dialog
from anyone who can't use them. The Sign-up page's Bypass action was already
admin-only end to end (the whole page is ClubAdminRequiredMixin-gated), so
no change in practice there.

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

club/models.py

@@ -422,12 +422,14 @@ class OnboardingRequirement(ClubScopedModel):
     requires_document = models.BooleanField(_("requires a document"), default=False, help_text=_("Staff can attach a file (e.g. the certificate itself) when marking this complete."))
     blocked_event_kinds = models.JSONField(_("blocks selection for"), default=list, blank=True, help_text=_("Event kinds a member can't be invited to or selected for while this is open. Empty means purely informational."))
     is_active = models.BooleanField(_("active"), default=True, help_text=_("Inactive requirements no longer apply to new memberships, but existing statuses are kept."))
-    order = models.PositiveIntegerField(_("order"), default=0, help_text=_("Lower numbers show first on the checklist."))
 
     class Meta:
         verbose_name = _("onboarding requirement")
         verbose_name_plural = _("onboarding requirements")
-        ordering = ["order", "name"]
+        # Alphabetical, not a configurable sequence: every active requirement
+        # blocks equally and there's no set order to complete them in, so
+        # ordering here is purely for a stable, predictable listing.
+        ordering = ["name"]
         constraints = [
             models.UniqueConstraint(fields=["club", "name"], name="unique_onboarding_requirement_name_per_club"),
         ]