Add invitation letter request flag to Grant admin

Display a boolean flag in the Grant admin change list view that indicates
whether a request for an invitation letter has been submitted. This helps
administrators quickly identify which grants have associated invitation
letter requests.

Changes:
- Added has_invitation_letter_request() method to Grant model
- Added has_invitation_letter_request_flag display method to GrantAdmin
- Added flag to admin list_display with 📧 emoji icon

Fixes #4384

Co-authored-by: Marco Acierno <[email protected]>

Author: claude[bot]

backend/grants/admin.py

@@ -402,6 +402,7 @@ class GrantAdmin(ExportMixin, ConferencePermissionMixin, admin.ModelAdmin):
         "country",
         "is_proposed_speaker",
         "is_confirmed_speaker",
+        "has_invitation_letter_request_flag",
         "emoji_gender",
         "conference",
         "status",
@@ -584,6 +585,11 @@ def user_has_ticket(self, obj: Grant) -> bool:
     def has_voucher(self, obj: Grant) -> bool:
         return obj.has_voucher
 
+    @admin.display(description="📧", boolean=True)
+    def has_invitation_letter_request_flag(self, obj: Grant) -> bool:
+        """Display flag indicating if user has submitted an invitation letter request"""
+        return obj.has_invitation_letter_request()
+
     def get_queryset(self, request):
         qs = (
             super()

backend/grants/models.py

@@ -333,6 +333,17 @@ def has_approved_accommodation(self):
     def current_or_pending_status(self):
         return self.pending_status or self.status
 
+    def has_invitation_letter_request(self):
+        """Check if user has submitted an invitation letter request for this conference"""
+        if not self.user_id:
+            return False
+        
+        from visa.models import InvitationLetterRequest
+        return InvitationLetterRequest.objects.filter(
+            conference=self.conference,
+            requester=self.user
+        ).exists()
+
 
 class GrantConfirmPendingStatusProxy(Grant):
     class Meta: