Use system actor for email uniqueness validation

Update email validation modules to use system actor for queries.
This ensures data integrity checks always run regardless of user permissions.

lib/mv/accounts/user/validations/email_not_used_by_other_member.ex

@@ -73,12 +73,18 @@ defmodule Mv.Accounts.User.Validations.EmailNotUsedByOtherMember do
   end
 
   defp check_email_uniqueness(email, exclude_member_id) do
+    alias Mv.Helpers
+    alias Mv.Helpers.SystemActor
+
     query =
       Mv.Membership.Member
       |> Ash.Query.filter(email == ^to_string(email))
       |> maybe_exclude_id(exclude_member_id)
 
-    case Ash.read(query) do
+    system_actor = SystemActor.get_system_actor()
+    opts = Helpers.ash_actor_opts(system_actor)
+
+    case Ash.read(query, opts) do
       {:ok, []} ->
         :ok