ML-168: broadcast index_changed event after background import

Import workers now broadcast :records_index_changed on
"records:index_changed" after successful import via
Records.broadcast_index_changed/0.

CollectionLive.Index and WishlistLive.Index subscribe to the
topic in mount/3 and reload their record streams on receipt,
with a live_action guard to skip reloads when the grid is
hidden behind a modal (:import, :barcode_scan).

IndexActions.handle_index_changed/1 refreshes total_entries
before reloading to keep the pagination bar accurate.

lib/music_library/records.ex

@@ -126,4 +126,21 @@ defmodule MusicLibrary.Records do
       {:update, record}
     )
   end
+
+  @doc """
+  Broadcasts that the records index has changed (new record imported, deleted, etc.).
+  Index LiveViews subscribe to this topic to auto-refresh.
+  """
+  @spec broadcast_index_changed() :: :ok
+  def broadcast_index_changed do
+    Phoenix.PubSub.broadcast(MusicLibrary.PubSub, "records:index_changed", :records_index_changed)
+  end
+
+  @doc """
+  Subscribes the calling process to records index change notifications.
+  """
+  @spec subscribe_to_index() :: :ok | {:error, term()}
+  def subscribe_to_index do
+    Phoenix.PubSub.subscribe(MusicLibrary.PubSub, "records:index_changed")
+  end
 end

lib/music_library/worker/import_from_musicbrainz_release.ex

@@ -7,6 +7,7 @@ defmodule MusicLibrary.Worker.ImportFromMusicbrainzRelease do
 
   use Oban.Worker, queue: :music_brainz, max_attempts: 3
 
+  alias MusicLibrary.Records
   alias MusicLibrary.Records.Record
   alias MusicLibrary.Worker.ErrorHandler
 
@@ -19,8 +20,12 @@ defmodule MusicLibrary.Worker.ImportFromMusicbrainzRelease do
     ]
 
     case MusicLibrary.Records.import_from_musicbrainz_release(release_id, opts) do
-      {:ok, _record} -> :ok
-      other -> ErrorHandler.to_oban_result(other)
+      {:ok, _record} ->
+        Records.broadcast_index_changed()
+        :ok
+
+      other ->
+        ErrorHandler.to_oban_result(other)
     end
   end
 end

lib/music_library/worker/import_from_musicbrainz_release_group.ex

@@ -23,8 +23,12 @@ defmodule MusicLibrary.Worker.ImportFromMusicbrainzReleaseGroup do
     ]
 
     case Records.import_from_musicbrainz_release_group(release_group_id, opts) do
-      {:ok, _record} -> :ok
-      other -> ErrorHandler.to_oban_result(other)
+      {:ok, _record} ->
+        Records.broadcast_index_changed()
+        :ok
+
+      other ->
+        ErrorHandler.to_oban_result(other)
     end
   end
 end