fix(radio): queue navigation, dedup, and similar-first variety (#500) (#503)

* fix(radio): queue navigation, dedup, and similar-first variety (#500)

After a Radio session ran a while, three things broke:

Queue navigation through duplicates. playTrack re-resolved the active
queue index by `findIndex(t.id === track.id)`, returning the *first*
matching id, so reaching the second occurrence of a track snapped
queueIndex back to the earlier slot — highlight jumped and the next
advance played the wrong follow-up. Added an optional
`targetQueueIndex` to playTrack, threaded through next(), previous(),
the audio:ended repeat-one path, queue-row click, and the queue-item
context menu. findIndex stays as the fallback for callers that just
have a track and a fresh queue.

Queue accumulation. enqueueRadio didn't dedupe incoming tracks; the
next() top-up deduped against the live queue but trimmed the played
tail down to HISTORY_KEEP=5, so a song heard 8 ago was gone from
`existingIds` and a later Last.fm/topSongs response could re-add it;
and the `.filter(...)` pass admitted intra-batch repeats (top +
similar overlap is common) because it read the dedup set before
mutating it. A module-level radioSessionSeenIds set, fed by
enqueueRadio and both top-up paths and reset on artist change and
clearQueue, closes all three: trimmed ids stay in the set, ids about
to be replaced (fresh enqueueRadio wiping the pending radio block)
are removed first so callers can re-introduce them, and the dedup
pass mutates the set inline.

Variety. Starting Radio on a track stacked five top tracks of the
seed artist before any similar-artist material played. Switched the
seed path and both top-up paths to lead with similar songs (other
artists) and only fall back to top tracks when similar comes back
empty — preserves the "no Last.fm" graceful degradation but stops
the seed artist from monopolising the front of the queue.

Not affected: gapless audio:track_switched (already index-based, no
findIndex), AudioMuse Instant Mix / Lucky Mix (single-element queues
or enqueue-only paths), the artist-radio path (no seedTrack — already
picks just one top track and fills the rest from similar).

Reported by netherguy4.

* docs: changelog entry for PR #503

Logs the radio queue navigation/dedup/similar-first fix in v1.46.0
"## Fixed".

src/components/QueuePanel.tsx

@@ -1063,7 +1063,9 @@ function QueuePanelHostOrSolo() {
                 className={`queue-item ${isPlaying ? 'active' : ''} ${contextMenu.isOpen && contextMenu.type === 'queue-item' && contextMenu.queueIndex === idx ? 'context-active' : ''}`}
                 onClick={() => {
                   suppressNextAutoScrollRef.current = true;
-                  playTrack(track, queue);
+                  // Pass the row index so a click on a duplicate track lands on
+                  // *this* slot, not the first occurrence (issue #500).
+                  playTrack(track, queue, undefined, undefined, idx);
                 }}
                 onContextMenu={(e) => {
                   e.preventDefault();