feat: implement photo albums (media groups) and persist account selection

Group photos with shared media_album_id into single album bubbles with
grid layout (up to 3x cols). Album navigation treats grouped photos as
one unit (j/k skip entire album). Persist selected account to
accounts.toml so it survives app restart.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/tdlib/messages/convert.rs

@@ -30,7 +30,8 @@ impl MessageManager {
             .text(content_text)
             .entities(entities)
             .date(msg.date)
-            .edit_date(msg.edit_date);
+            .edit_date(msg.edit_date)
+            .media_album_id(msg.media_album_id);
 
         if msg.is_outgoing {
             builder = builder.outgoing();