refactor: add typespecs and module constants

- Add @spec for public functions in Member and UserLive.Form
- Replace magic numbers with module constants:
  - @member_search_limit = 10
  - @default_similarity_threshold = 0.2
- Add comprehensive @doc for filter_by_email_match and fuzzy_search

lib/mv_web/live/user_live/form.ex

@@ -267,6 +267,7 @@ defmodule MvWeb.UserLive.Form do
      |> assign_form()}
   end
 
+  @spec return_to(String.t() | nil) :: String.t()
   defp return_to("show"), do: "show"
   defp return_to(_), do: "index"
 
@@ -383,8 +384,10 @@ defmodule MvWeb.UserLive.Form do
     {:noreply, socket}
   end
 
+  @spec notify_parent(any()) :: any()
   defp notify_parent(msg), do: send(self(), {__MODULE__, msg})
 
+  @spec assign_form(Phoenix.LiveView.Socket.t()) :: Phoenix.LiveView.Socket.t()
   defp assign_form(%{assigns: %{user: user, show_password_fields: show_password_fields}} = socket) do
     form =
       if user do
@@ -404,10 +407,11 @@ defmodule MvWeb.UserLive.Form do
     assign(socket, form: to_form(form))
   end
 
+  @spec return_path(String.t(), Mv.Accounts.User.t() | nil) :: String.t()
   defp return_path("index", _user), do: ~p"/users"
   defp return_path("show", user), do: ~p"/users/#{user.id}"
 
-  # Load initial members when the form is loaded or member is unlinked
+  @spec load_initial_members(Phoenix.LiveView.Socket.t()) :: Phoenix.LiveView.Socket.t()
   defp load_initial_members(socket) do
     user = socket.assigns.user
     user_email = if user, do: user.email, else: nil
@@ -421,7 +425,8 @@ defmodule MvWeb.UserLive.Form do
     |> assign(show_member_dropdown: false)
   end
 
-  # Load members based on search query
+  @spec load_available_members(Phoenix.LiveView.Socket.t(), String.t()) ::
+          Phoenix.LiveView.Socket.t()
   defp load_available_members(socket, query) do
     user = socket.assigns.user
     user_email = if user, do: user.email, else: nil
@@ -430,7 +435,7 @@ defmodule MvWeb.UserLive.Form do
     assign(socket, available_members: members)
   end
 
-  # Query available members using the Ash action
+  @spec load_members_for_linking(String.t() | nil, String.t() | nil) :: [Mv.Membership.Member.t()]
   defp load_members_for_linking(user_email, search_query) do
     user_email_str = if user_email, do: to_string(user_email), else: nil
     search_query_str = if search_query && search_query != "", do: search_query, else: nil