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/member_live/index.ex

@@ -58,9 +58,8 @@ defmodule MvWeb.MemberLive.Index do
   @impl true
   def mount(_params, session, socket) do
     # Load custom fields that should be shown in overview (for display)
-    # Note: Using Ash.read! (bang version) - errors will be handled by Phoenix LiveView
-    # and result in a 500 error page. This is appropriate for LiveViews where errors
-    # should be visible to the user rather than silently failing.
+    # Errors in mount are handled by Phoenix LiveView and result in a 500 error page.
+    # This is appropriate for initialization errors that should be visible to the user.
     actor = current_actor(socket)
 
     custom_fields_visible =
@@ -727,8 +726,7 @@ defmodule MvWeb.MemberLive.Index do
         socket.assigns.custom_fields_visible
       )
 
-    # Note: Using Ash.read! - errors will be handled by Phoenix LiveView
-    # This is appropriate for data loading in LiveViews
+    # Errors in handle_params are handled by Phoenix LiveView
     actor = current_actor(socket)
     members = Ash.read!(query, actor: actor)