refactor(member-live): modularize the overview and drop the superseded in-memory paths

Extract the cookie parser, export-payload builder and fee-status helper
into their own modules and remove the filter/sort/load helpers the
database pushdown made dead, so the overview LiveView stays a thin
coordinator over focused units.

test/mv_web/live/member_live/index/cookie_test.exs

@@ -0,0 +1,22 @@
+defmodule MvWeb.MemberLive.Index.CookieTest do
+  @moduledoc """
+  Tests for the shared cookie-header parser used by the overview persistence chain.
+  """
+  use ExUnit.Case, async: true
+
+  alias MvWeb.MemberLive.Index.Cookie
+
+  describe "parse_header/1" do
+    test "splits pairs and URL-decodes values" do
+      assert Cookie.parse_header("a=1; b=hello%20world") == %{"a" => "1", "b" => "hello world"}
+    end
+
+    test "maps a valueless entry to an empty string" do
+      assert Cookie.parse_header("flag; a=1") == %{"flag" => "", "a" => "1"}
+    end
+
+    test "keeps only the first '=' as the separator" do
+      assert Cookie.parse_header("token=a=b=c") == %{"token" => "a=b=c"}
+    end
+  end
+end