Coach mode: bench-attendance filter overhaul, squad player detail, add-staff

- Attendance sheet: "All"/"Goalies" chips replaced with "Responded" (the
  new default -- present/selected/maybe) and "Silent"; goalies are just
  another player for a practice, and neither silent nor declined members
  are expected to show up, so the default view skips both.
- Today's KPI header gains an "Out" tile alongside Squad/In/Silent.
- Squad screen: each roster row now opens a per-player detail sheet with
  season attendance stats, tap-to-call buttons (the player's own phone/
  emergency phone, plus each guardian's for a child), and -- for whoever
  manages the team -- the position/jersey/captaincy edit and a remove-
  from-roster action that used to be desktop-only.
- Staff section gets its own "Add" entry point, mirroring the roster's
  bulk-add flow with a shared position picker (StaffAssignment.position
  is required, unlike a roster spot's).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

mobile/forms.py

@@ -1,6 +1,8 @@
 from django import forms
+from django.utils.translation import gettext_lazy as _
 
 from members.models import Member
+from teams.models import Position, TeamMembership
 
 #: Shared by every text-ish field below -- mobile has no equivalent of
 #: management/controlpanel's templatetags/field.html (which builds widget
@@ -37,3 +39,37 @@ class MemberProfileForm(forms.ModelForm):
         super().__init__(*args, **kwargs)
         for field in self.fields.values():
             field.widget.attrs["class"] = _INPUT_CLASSES
+
+
+class CoachRosterEditForm(forms.ModelForm):
+    """Coach-mode roster row edit -- mobile/coach/roster_member.html's player
+    detail sheet. Same fields management.forms.TeamMembershipForm edits,
+    minus ``member`` (fixed by the URL here, never reassigned from this
+    screen) -- this used to be a desktop-only action; see CoachSquadView's
+    own docstring for why that changed."""
+
+    class Meta:
+        model = TeamMembership
+        fields = ["position", "jersey_number", "is_captain", "is_alternate_captain"]
+
+    def __init__(self, *args, club=None, team=None, season=None, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.team = team
+        self.season = season
+        self.fields["position"].queryset = Position.objects.filter(club=club, staff_position=False)
+        self.fields["position"].required = True
+        self.fields["position"].widget.attrs["class"] = _INPUT_CLASSES
+        self.fields["jersey_number"].widget.attrs["class"] = _INPUT_CLASSES
+        self.fields["is_captain"].widget.attrs["class"] = "h-5 w-5 shrink-0 accent-ink"
+        self.fields["is_alternate_captain"].widget.attrs["class"] = "h-5 w-5 shrink-0 accent-ink"
+
+    def clean(self):
+        # Same jersey-clash check as TeamMembershipForm.clean -- team/season aren't
+        # form fields, so Django's automatic validate_unique() can't catch this itself.
+        cleaned = super().clean()
+        jersey_number = cleaned.get("jersey_number")
+        if jersey_number is not None and self.team is not None and self.season is not None:
+            clash = TeamMembership.objects.filter(team=self.team, season=self.season, jersey_number=jersey_number).exclude(pk=self.instance.pk).exists()
+            if clash:
+                self.add_error("jersey_number", _("Another player on this team already has this jersey number this season."))
+        return cleaned