feat(admin): improve user admin list view and detail page

Add is_superuser to list_display and list_filter. Add is_active,
is_staff, is_superuser, last_login (readonly), and user_permissions
to the user detail fieldset.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

gaehsnitz/admin.py

@@ -47,9 +47,9 @@ class SetPinForm(forms.Form):
 
 @admin.register(User)
 class CustomUserAdmin(UserAdmin):
-    list_display = ("username", "is_staff", "consumed_drinks_price", "paid_amount", "open_balance")
+    list_display = ("username", "is_staff", "is_superuser", "consumed_drinks_price", "paid_amount", "open_balance")
     ordering = ("username",)
-    list_filter = ["is_staff"]
+    list_filter = ["is_staff", "is_superuser"]
     fieldsets = (
         (
             None,
@@ -58,6 +58,11 @@ class CustomUserAdmin(UserAdmin):
                     "username",
                     "password",
                     "pin_status",
+                    "is_active",
+                    "is_staff",
+                    "is_superuser",
+                    "last_login",
+                    "user_permissions",
                 )
             },
         ),
@@ -79,6 +84,7 @@ class CustomUserAdmin(UserAdmin):
         "paid_amount",
         "open_balance",
         "pin_status",
+        "last_login",
         "drinks_breakdown",
         "free_drinks_breakdown",
     )