refactor: Replace bang calls with error handling in Index LiveViews

- Replace Ash.get!/Ash.destroy! with Ash.get/Ash.destroy
- Add case statements for Forbidden, NotFound, and generic errors
- Display user-friendly flash messages for all error cases
- Use Enum.map_join/3 for efficient error formatting

lib/mv_web/live/role_live/index.ex

@@ -118,7 +118,7 @@ defmodule MvWeb.RoleLive.Index do
 
   @spec load_roles(map() | nil) :: [Mv.Authorization.Role.t()]
   defp load_roles(actor) do
-    opts = if actor, do: [actor: actor], else: []
+    opts = MvWeb.LiveHelpers.ash_actor_opts(actor)
 
     case Authorization.list_roles(opts) do
       {:ok, roles} -> Enum.sort_by(roles, & &1.name)