refactor(member-live): modularize the overview and drop the superseded in-memory paths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

lib/mv_web/live/member_live/index/cookie.ex

@@ -0,0 +1,28 @@
+defmodule MvWeb.MemberLive.Index.Cookie do
+  @moduledoc """
+  Shared cookie-header parsing for the member-overview persistence chain.
+
+  Both `MvWeb.MemberLive.Index.ViewSettings` and
+  `MvWeb.MemberLive.Index.FieldSelection` read their persisted value from the
+  raw request `Cookie:` header on the disconnected mount, so the parsing lives
+  here once.
+  """
+
+  @doc """
+  Parses a raw `Cookie:` request-header string into a `%{name => value}` map,
+  URL-decoding each value. A valueless entry (`"key"`) maps to `""`; malformed
+  segments are skipped.
+  """
+  @spec parse_header(String.t()) :: %{String.t() => String.t()}
+  def parse_header(cookie_header) when is_binary(cookie_header) do
+    cookie_header
+    |> String.split(";")
+    |> Enum.map(&String.trim/1)
+    |> Enum.map(&String.split(&1, "=", parts: 2))
+    |> Enum.reduce(%{}, fn
+      [key, value], acc -> Map.put(acc, key, URI.decode(value))
+      [key], acc -> Map.put(acc, key, "")
+      _, acc -> acc
+    end)
+  end
+end