fix: prevent deadlocks by detecting existing transactions

lib/membership/member.ex

@@ -763,7 +763,7 @@ defmodule Mv.Membership.Member do
   end
 
   # Regenerates cycles with new type/amount
-  # CycleGenerator uses its own transaction with advisory lock
+  # CycleGenerator detects if already in transaction and uses advisory lock accordingly
   defp regenerate_cycles(member_id) do
     case Mv.MembershipFees.CycleGenerator.generate_cycles_for_member(member_id) do
       {:ok, _cycles} -> :ok