fix(ephemeral): replace 1 << 48 with 2 ** 48 for ephemeral track id floor

JavaScript bitwise shift operates on 32-bit signed integers, so
`1 << 48` is `1 << (48 % 32)` = `1 << 16` = 65536. Every Qobuz track
id sits above that, so the existing `id >= EPHEMERAL_ID_FLOOR` checks
were classifying every Qobuz track as ephemeral and disabling the
favorite / playlist / mixtape / collection actions for them — most
visibly in the immersive player favorite button, but also silently
stripping Qobuz tracks from the persisted session queue.

Five places shared the same broken constant, all now use `2 ** 48`
(281474976710656) — the actual ephemeral id floor defined in
src-tauri/src/ephemeral_library/mod.rs:

  - src/routes/+page.svelte (two metadataActionsDisabled checks for
    the immersive player and now-playing bar, plus the session-save
    EPHEMERAL_ID_FLOOR filter).
  - src/lib/components/QueuePanel.svelte (isEphemeralQueueTrack guard
    that hides favorite / playlist / track-info actions for queue
    rows).
  - src/lib/stores/playerStore.ts (isEphemeralTransition flag in the
    gapless carve-out and CUE virtual-track position translation).
  - src/lib/components/views/LocalLibraryView.svelte (close-folder
    cleanup check — only ephemeral folders should wipe the queue +
    now-playing slot when closed).

Each call site keeps a short comment naming the trap so future edits
don't reach for the same bitwise expression.

cc

src/routes/+page.svelte

@@ -4474,7 +4474,10 @@
       // Strip them from the persisted queue and clear the current-index
       // pointer if it was sitting on one — the ephemeral pane comes back
       // via folder-path persistence and the user re-clicks play.
-      const EPHEMERAL_ID_FLOOR = 1 << 48;
+      // 2 ** 48 (NOT 1 << 48 — JavaScript bitwise shift operates on
+      // 32-bit ints so 1 << 48 silently truncates to 65536, which
+      // mis-classified every Qobuz track as ephemeral).
+      const EPHEMERAL_ID_FLOOR = 2 ** 48;
       const persistedTracks: PersistedQueueTrack[] = [];
       let persistedCurrentIndex: number | null = null;
       for (let i = 0; i < tracks.length; i++) {
@@ -6884,7 +6887,7 @@
         {isFavorite}
         onToggleFavorite={toggleFavorite}
         onAddToPlaylist={openAddToPlaylistModal}
-        metadataActionsDisabled={currentTrack != null && currentTrack.id >= (1 << 48)}
+        metadataActionsDisabled={currentTrack != null && currentTrack.id >= 2 ** 48}
         onOpenQueue={toggleQueue}
         onOpenMiniPlayer={() => {
           void enterMiniplayerMode();
@@ -6990,7 +6993,7 @@
         onToggleRepeat={toggleRepeat}
         {isFavorite}
         onToggleFavorite={toggleFavorite}
-        metadataActionsDisabled={currentTrack != null && currentTrack.id >= (1 << 48)}
+        metadataActionsDisabled={currentTrack != null && currentTrack.id >= 2 ** 48}
         lyricsLines={lyricsLines}
         lyricsActiveIndex={lyricsActiveIndex}
         lyricsActiveProgress={lyricsActiveProgress}