Fix favorite heart state resetting on queue updates for radio and provider items

[dmoo500]

Problem

When a radio station or provider track (not yet in the library) was playing and the user favorited it, the heart button in the fullscreen player would briefly light up and then reset to empty. This happened on every subsequent queue update from the server.

Root cause: store.curQueueItem is derived from activePlayerQueue.current_item, which the server pushes as a complete replacement object on every queue event. When the item was enqueued with favorite: false, all server-side queue updates kept sending that original value — overwriting any optimistic local change made by toggleFavorite.

Library tracks that were already favorited before being enqueued were not affected because their favorite: true was baked in at enqueue time.

Fix

Introduce a local currentItemFavorite ref that lives independently of the server-pushed media_item object:

• Initialised from media_item.favorite whenever the queue item changes (watch on queue_item_id)
• Optimistically updated to true/false in onHeartBtnClick — survives server queue refreshes because it is not part of the replaced object
• Synced from server via a MEDIA_ITEM_UPDATED subscription: when the server confirms the favorite change (URI match), currentItemFavorite is updated to the server's value

The template heart fill and the "already favorited" branch in onHeartBtnClick now read currentItemFavorite instead of store.curQueueItem?.media_item?.favorite.