Fix stale PubSub subscriptions on record navigation

Subscription management was only done in mount/3, meaning
navigating to a different record via handle_params/3 left the
old subscription active. A background update for the old record
would then overwrite the currently displayed record.

Fix: manage subscriptions in handle_params/3 (unsubscribe old,
subscribe new) via shared RecordActions.manage_subscription/2,
and guard handle_info({:update,...}) against mismatched IDs.

lib/music_library_web/live/collection_live/show.ex

@@ -348,11 +348,7 @@ defmodule MusicLibraryWeb.CollectionLive.Show do
   end
 
   @impl true
-  def mount(%{"id" => record_id}, _session, socket) do
-    if connected?(socket) do
-      Records.subscribe(record_id)
-    end
-
+  def mount(_params, _session, socket) do
     {:ok,
      socket
      |> assign(:current_section, :collection)
@@ -362,6 +358,8 @@ defmodule MusicLibraryWeb.CollectionLive.Show do
 
   @impl true
   def handle_params(%{"id" => id}, _, socket) do
+    RecordActions.manage_subscription(socket, id)
+
     record = Records.get_record!(id)
     last_listened_track = ListeningStats.get_last_listened_track(record)
     play_count = ListeningStats.play_count(record)
@@ -474,10 +472,14 @@ defmodule MusicLibraryWeb.CollectionLive.Show do
 
   @impl true
   def handle_info({:update, record}, socket) do
-    {:noreply,
-     socket
-     |> RecordActions.handle_record_updated(record)
-     |> assign_similar_records()}
+    if record.id == socket.assigns.record.id do
+      {:noreply,
+       socket
+       |> RecordActions.handle_record_updated(record)
+       |> assign_similar_records()}
+    else
+      {:noreply, socket}
+    end
   end
 
   defp page_title(action, record) do

lib/music_library_web/live/wishlist_live/show.ex

@@ -284,13 +284,9 @@ defmodule MusicLibraryWeb.WishlistLive.Show do
   end
 
   @impl true
-  def mount(%{"id" => record_id}, _session, socket) do
+  def mount(_params, _session, socket) do
     current_date = DateTime.utc_now() |> DateTime.to_date()
 
-    if connected?(socket) do
-      Records.subscribe(record_id)
-    end
-
     {:ok,
      socket
      |> assign(current_section: :wishlist)
@@ -299,6 +295,8 @@ defmodule MusicLibraryWeb.WishlistLive.Show do
 
   @impl true
   def handle_params(%{"id" => id}, _, socket) do
+    RecordActions.manage_subscription(socket, id)
+
     record = Records.get_record!(id)
     online_store_templates = OnlineStoreTemplates.list_enabled_templates()
 
@@ -367,7 +365,11 @@ defmodule MusicLibraryWeb.WishlistLive.Show do
 
   @impl true
   def handle_info({:update, record}, socket) do
-    {:noreply, RecordActions.handle_record_updated(socket, record)}
+    if record.id == socket.assigns.record.id do
+      {:noreply, RecordActions.handle_record_updated(socket, record)}
+    else
+      {:noreply, socket}
+    end
   end
 
   defp page_title(action, record) do